brew install gtk-doc --verbose log

$ brew --config
HOMEBREW_VERSION: 0.9.4
ORIGIN: https://github.com/mxcl/homebrew.git
HEAD: 6914aa5e5d81ab7fe9d758e21538790e25c5ed80
HOMEBREW_PREFIX: /usr/local
HOMEBREW_CELLAR: /usr/local/Cellar
CPU: quad-core 64-bit sandybridge
OS X: 10.7.5-x86_64
Xcode: 4.6.2
CLT: 4.6.0.0.1.1365549073
LLVM-GCC: build 2336
Clang: 4.2 build 425
X11: 2.6.5 => /usr/X11
System Ruby: 1.8.7-358
Perl: /usr/bin/perl
Python: /usr/local/bin/python => /usr/local/Cellar/python/2.7.5/Frameworks/Python.framework/Versions/2.7/bin/python2.7
Ruby: /Users/admin/.rbenv/shims/ruby
$ brew install gtk-doc --verbose
/usr/bin/env perl -e use XML::Parser
==> Writing /usr/local/lib/python2.7/site-packages/sitecustomize.py
==> Writing /usr/local/Cellar/python/2.7.5/Frameworks/Python.framework/Versions/2.7/lib/python2.7/distutils/distutils.cfg
/usr/bin/env perl -e use XML::Parser
==> Downloading http://ftp.gnome.org/pub/GNOME/sources/gtk-doc/1.18/gtk-doc-1.18.tar.bz2
Already downloaded: /Library/Caches/Homebrew/gtk-doc-1.18.tar.bz2
tar xf /Library/Caches/Homebrew/gtk-doc-1.18.tar.bz2
==> ./configure --disable-debug --disable-dependency-tracking --prefix=/usr/local/Cellar/gtk-doc/1.18 --disable-scrollkeeper --with-xml-catalog=/usr/local/etc/xml/catalog
./configure --disable-debug --disable-dependency-tracking --prefix=/usr/local/Cellar/gtk-doc/1.18 --disable-scrollkeeper --with-xml-catalog=/usr/local/etc/xml/catalog
checking for a BSD-compatible install... /usr/bin/install -c
checking whether build environment is sane... yes
checking for a thread-safe mkdir -p... build-aux/install-sh -c -d
checking for gawk... no
checking for mawk... no
checking for nawk... no
checking for awk... awk
checking whether make sets $(MAKE)... yes
checking how to create a ustar tar archive... gnutar
checking whether to disable maintainer-specific portions of Makefiles... yes
checking whether ln -s works... yes
checking for pkg-config... /usr/local/opt/pkg-config/bin/pkg-config
checking pkg-config is at least version 0.9.0... yes
checking gnome-doc-utils >= 0.3.2... yes
checking for gcc... cc
checking whether the C compiler works... yes
checking for C compiler default output file name... a.out
checking for suffix of executables... 
checking whether we are cross compiling... no
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether cc accepts -g... yes
checking for cc option to accept ISO C89... none needed
checking for style of include used by make... GNU
checking dependency style of cc... none
checking build system type... i386-apple-darwin11.4.2
checking host system type... i386-apple-darwin11.4.2
checking for a sed that does not truncate output... /usr/local/Library/ENV/4.3/sed
checking for grep that handles long lines and -e... /usr/bin/grep
checking for egrep... /usr/bin/grep -E
checking for fgrep... /usr/bin/grep -F
checking for ld used by cc... /usr/bin/ld
checking if the linker (/usr/bin/ld) is GNU ld... no
checking for BSD- or MS-compatible name lister (nm)... /usr/bin/nm
checking the name lister (/usr/bin/nm) interface... BSD nm
checking the maximum length of command line arguments... 196608
checking whether the shell understands some XSI constructs... yes
checking whether the shell understands "+="... yes
checking for /usr/bin/ld option to reload object files... -r
checking for objdump... no
checking how to recognize dependent libraries... pass_all
checking for ar... ar
checking for strip... strip
checking for ranlib... ranlib
checking command to parse /usr/bin/nm output from cc object... ok
checking for dsymutil... dsymutil
checking for nmedit... nmedit
checking for lipo... lipo
checking for otool... otool
checking for otool64... no
checking for -single_module linker flag... yes
checking for -exported_symbols_list linker flag... yes
checking how to run the C preprocessor... cc -E
checking for ANSI C header files... yes
checking for sys/types.h... yes
checking for sys/stat.h... yes
checking for stdlib.h... yes
checking for string.h... yes
checking for memory.h... yes
checking for strings.h... yes
checking for inttypes.h... yes
checking for stdint.h... yes
checking for unistd.h... yes
checking for dlfcn.h... yes
checking for objdir... .libs
checking if cc supports -fno-rtti -fno-exceptions... yes
checking for cc option to produce PIC... -fno-common -DPIC
checking if cc PIC flag -fno-common -DPIC works... yes
checking if cc static flag -static works... no
checking if cc supports -c -o file.o... yes
checking if cc supports -c -o file.o... (cached) yes
checking whether the cc linker (/usr/bin/ld) supports shared libraries... yes
checking dynamic linker characteristics... darwin11.4.2 dyld
checking how to hardcode library paths into programs... immediate
checking whether stripping libraries is possible... yes
checking if libtool supports shared libraries... yes
checking whether to build shared libraries... yes
checking whether to build static libraries... yes
checking for pkg-config... (cached) /usr/local/opt/pkg-config/bin/pkg-config
checking pkg-config is at least version 0.19... yes
checking for perl... /usr/bin/perl
checking if Perl version >= 5.6.0... yes
checking for a Python interpreter with version >= 2.3... python
checking for python... /usr/local/opt/python/bin/python
checking for python version... 2.7
checking for python platform... darwin
checking for python script directory... ${prefix}/lib/python2.7/site-packages
checking for python extension module directory... ${exec_prefix}/lib/python2.7/site-packages
checking for openjade... no
checking for jade... no
configure: WARNING: Could not find openjade or jade, so SGML is not supported
checking for xsltproc... /usr/bin/xsltproc
checking for dblatex... no
checking for fop... no
configure: WARNING: neither dblatex nor fop found, so no pdf output from xml
checking for XML catalog (/usr/local/etc/xml/catalog)... found
checking for xmlcatalog... /usr/local/opt/libxml2/bin/xmlcatalog
checking for DocBook XML DTD V4.3 in XML catalog... found
checking for DocBook XSL Stylesheets in XML catalog... found
checking for source-highlight... no
checking for highlight... no
checking for vim... /usr/bin/vim
checking whether vim has +syntax feature... yes
checking for TEST_DEPS... yes
checking whether to enable runtime debugging code... no
configure: creating ./config.status
config.status: creating Makefile
config.status: creating gtk-doc.pc
config.status: creating gtk-doc.dsl
config.status: creating gtk-doc.spec
config.status: creating gtk-doc.cat
config.status: creating gtkdoc-common.pl
config.status: creating help/Makefile
config.status: creating help/manual/Makefile
config.status: creating tests/Makefile
config.status: creating tests/gobject/Makefile
config.status: creating tests/gobject/src/Makefile
config.status: creating tests/gobject/docs/Makefile
config.status: creating tests/gobject/docs-tmpl/Makefile
config.status: creating tests/bugs/Makefile
config.status: creating tests/bugs/src/Makefile
config.status: creating tests/bugs/docs/Makefile
config.status: creating tests/annotations/Makefile
config.status: creating tests/annotations/src/Makefile
config.status: creating tests/annotations/docs/Makefile
config.status: creating tests/fail/Makefile
config.status: creating tests/fail/src/Makefile
config.status: creating tests/fail/docs/Makefile
config.status: creating tests/empty/Makefile
config.status: creating tests/empty/src/Makefile
config.status: creating tests/empty/docs/Makefile
config.status: creating gtkdoc-check
config.status: creating gtkdoc-depscan
config.status: creating gtkdoc-fixxref
config.status: creating gtkdoc-mkdb
config.status: creating gtkdoc-mkhtml
config.status: creating gtkdoc-mkman
config.status: creating gtkdoc-mkpdf
config.status: creating gtkdoc-mktmpl
config.status: creating gtkdoc-rebase
config.status: creating gtkdoc-scan
config.status: creating gtkdoc-scangobj
config.status: creating gtkdoc-scanobj
config.status: creating gtkdocize
config.status: creating tests/tools.sh
config.status: executing depfiles commands
config.status: executing libtool commands
configure:
gtk-doc was configured with the following options:
==================================================
configure: ** Python based tools enabled, using /usr/local/opt/python/bin/python
configure:    SGML support disabled, no jade processor available
configure:    XML PDF support disabled, no fop available
configure: ** Gnome-doc-utils support enabled
configure:    Scrollkeeper support disabled
configure: ** Syntax highlighting of examples enabled, using /usr/bin/vim
configure: ** Building regression tests
configure:    Debug tracing disabled
==> make
make 
Making all in help
Making all in manual
msgfmt -o bn_IN/bn_IN.mo bn_IN/bn_IN.po
msgfmt -o en_GB/en_GB.mo en_GB/en_GB.po
msgfmt -o el/el.mo el/el.po
msgfmt -o de/de.mo de/de.po
msgfmt -o es/es.mo es/es.po
msgfmt -o fr/fr.mo fr/fr.po
msgfmt -o gu/gu.mo gu/gu.po
msgfmt -o sl/sl.mo sl/sl.po
msgfmt -o sv/sv.mo sv/sv.po
msgfmt -o te/te.mo te/te.po
msgfmt -o ta/ta.mo ta/ta.po
xsltproc -o gtk-doc-manual-C.omf --stringparam db2omf.basename gtk-doc-manual --stringparam db2omf.format 'docbook' --stringparam db2omf.dtd "-//OASIS//DTD DocBook XML V4.3//EN" --stringparam db2omf.lang C --stringparam db2omf.omf_dir "/usr/local/Cellar/gtk-doc/1.18/share/omf" --stringparam db2omf.help_dir "/usr/local/Cellar/gtk-doc/1.18/share/gnome/help" --stringparam db2omf.omf_in "/private/tmp/gtk-doc-sEyg/gtk-doc-1.18/help/manual/gtk-doc-manual.omf.in"  `/usr/local/opt/pkg-config/bin/pkg-config --variable db2omf gnome-doc-utils` C/gtk-doc-manual.xml || { rm -f "gtk-doc-manual-C.omf"; exit 1; }
if ! test -d bn_IN/; then mkdir bn_IN/; fi
if ! test -d de/; then mkdir de/; fi
if ! test -d el/; then mkdir el/; fi
if [ -f "C/gtk-doc-manual.xml" ]; then d="../"; else d="/private/tmp/gtk-doc-sEyg/gtk-doc-1.18/help/manual/"; fi; \
  mo="bn_IN/bn_IN.mo"; \
	if [ -f "${mo}" ]; then mo="../${mo}"; else mo="/private/tmp/gtk-doc-sEyg/gtk-doc-1.18/help/manual/${mo}"; fi; \
	(cd bn_IN/ && \
	  `which xml2po` -m docbook -e -t "${mo}" \
	    "${d}C/gtk-doc-manual.xml" > gtk-doc-manual.xml.tmp && \
	    cp gtk-doc-manual.xml.tmp gtk-doc-manual.xml && rm -f gtk-doc-manual.xml.tmp)
if [ -f "C/gtk-doc-manual.xml" ]; then d="../"; else d="/private/tmp/gtk-doc-sEyg/gtk-doc-1.18/help/manual/"; fi; \
	mo="el/el.mo"; \
	if [ -f "${mo}" ]; then mo="../${mo}"; else mo="/private/tmp/gtk-doc-sEyg/gtk-doc-1.18/help/manual/${mo}"; fi; \
	(cd el/ && \
	  `which xml2po` -m docbook -e -t "${mo}" \
	    "${d}C/gtk-doc-manual.xml" > gtk-doc-manual.xml.tmp && \
	    cp gtk-doc-manual.xml.tmp gtk-doc-manual.xml && rm -f gtk-doc-manual.xml.tmp)
if [ -f "C/gtk-doc-manual.xml" ]; then d="../"; else d="/private/tmp/gtk-doc-sEyg/gtk-doc-1.18/help/manual/"; fi; \
	mo="de/de.mo"; \
	if [ -f "${mo}" ]; then mo="../${mo}"; else mo="/private/tmp/gtk-doc-sEyg/gtk-doc-1.18/help/manual/${mo}"; fi; \
	(cd de/ && \
	  `which xml2po` -m docbook -e -t "${mo}" \
	    "${d}C/gtk-doc-manual.xml" > gtk-doc-manual.xml.tmp && \
	    cp gtk-doc-manual.xml.tmp gtk-doc-manual.xml && rm -f gtk-doc-manual.xml.tmp)
C/gtk-doc-manual.xml:9: warning: failed to load external entity "-//OASIS//DTD DocBook XML V4.3//EN"
]><!-- =============Document Header ============================= -->
  ^
if ! test -d en_GB/; then mkdir en_GB/; fi
if [ -f "C/gtk-doc-manual.xml" ]; then d="../"; else d="/private/tmp/gtk-doc-sEyg/gtk-doc-1.18/help/manual/"; fi; \
	mo="en_GB/en_GB.mo"; \
	if [ -f "${mo}" ]; then mo="../${mo}"; else mo="/private/tmp/gtk-doc-sEyg/gtk-doc-1.18/help/manual/${mo}"; fi; \
	(cd en_GB/ && \
	  `which xml2po` -m docbook -e -t "${mo}" \
	    "${d}C/gtk-doc-manual.xml" > gtk-doc-manual.xml.tmp && \
	    cp gtk-doc-manual.xml.tmp gtk-doc-manual.xml && rm -f gtk-doc-manual.xml.tmp)
Traceback (most recent call last):
  File "/usr/local/opt/gnome-doc-utils/bin/xml2po", line 191, in <module>
Traceback (most recent call last):
Traceback (most recent call last):
  File "/usr/local/opt/gnome-doc-utils/bin/xml2po", line 191, in <module>
  File "/usr/local/opt/gnome-doc-utils/bin/xml2po", line 191, in <module>
    main(sys.argv[1:])
      File "/usr/local/opt/gnome-doc-utils/bin/xml2po", line 88, in main
main(sys.argv[1:])
  File "/usr/local/opt/gnome-doc-utils/bin/xml2po", line 88, in main
    from xml2po import Main
    from xml2po import Main
ImportError: ImportError: No module named xml2poNo module named xml2po

    main(sys.argv[1:])
  File "/usr/local/opt/gnome-doc-utils/bin/xml2po", line 88, in main
    from xml2po import Main
ImportError: No module named xml2po
Traceback (most recent call last):
  File "/usr/local/opt/gnome-doc-utils/bin/xml2po", line 191, in <module>
    main(sys.argv[1:])
  File "/usr/local/opt/gnome-doc-utils/bin/xml2po", line 88, in main
    from xml2po import Main
ImportError: No module named xml2po
make[2]: *** [de/gtk-doc-manual.xml] Error 1
make[2]: *** Waiting for unfinished jobs....
make[2]: *** [el/gtk-doc-manual.xml] Error 1
make[2]: *** [en_GB/gtk-doc-manual.xml] Error 1
make[2]: *** [bn_IN/gtk-doc-manual.xml] Error 1
make[1]: *** [all-recursive] Error 1
make: *** [all-recursive] Error 1
==> Configuration
HOMEBREW_VERSION: 0.9.4
HEAD: 6914aa5e5d81ab7fe9d758e21538790e25c5ed80
CPU: quad-core 64-bit sandybridge
OS X: 10.7.5-x86_64
Xcode: 4.6.2
CLT: 4.6.0.0.1.1365549073
X11: 2.6.5 => /usr/X11
==> ENV
HOMEBREW_CC: clang
MAKEFLAGS: -j4
CMAKE_PREFIX_PATH: /usr/local/opt/gettext:/usr/local/opt/libxml2:/usr/local/opt/libffi:/usr/local
CMAKE_INCLUDE_PATH: /System/Library/Frameworks/OpenGL.framework/Versions/Current/Headers/:/usr/local/opt/python/Frameworks/Python.framework/Versions/2.7/Headers
CMAKE_LIBRARY_PATH: /System/Library/Frameworks/OpenGL.framework/Versions/Current/Libraries
CMAKE_FRAMEWORK_PATH: /usr/local/Frameworks
PKG_CONFIG_PATH: /usr/local/opt/libxml2/lib/pkgconfig:/usr/local/opt/libffi/lib/pkgconfig:/usr/local/opt/glib/lib/pkgconfig:/usr/local/opt/gnome-doc-utils/share/pkgconfig:/usr/local/opt/python/Frameworks/Python.framework/Versions/2.7/lib/pkgconfig
PKG_CONFIG_LIBDIR: /usr/lib/pkgconfig
ACLOCAL_PATH: /usr/local/opt/gettext/share/aclocal:/usr/local/opt/libxml2/share/aclocal:/usr/local/share/aclocal
OBJC: cc
PATH: /usr/local/opt/python/bin:/usr/local/Library/ENV/4.3:/usr/local/opt/pkg-config/bin:/usr/local/opt/gettext/bin:/usr/local/opt/libxml2/bin:/usr/local/opt/gnome-doc-utils/bin:/usr/local/opt/glib/bin:/usr/local/opt/docbook-xsl/bin:/usr/bin:/bin:/usr/sbin:/sbin

Error: gtk-doc did not build
Logs:       /Users/admin/Library/Logs/Homebrew/gtk-doc/config.log

These open issues may also help:
    https://github.com/mxcl/homebrew/issues/20150