Problem with logspout custom build

gistfile1.txt

logspout-kafka|master ⇒ docker build -t gettyimages/logspout -f Dockerfile.example .
Sending build context to Docker daemon 71.68 kB
Sending build context to Docker daemon 
Step 0 : FROM gliderlabs/logspout:master
# Executing 2 build triggers
Trigger 0, COPY ./modules.go /src/modules.go
Step 0 : COPY ./modules.go /src/modules.go
 ---> Using cache
Trigger 1, RUN cd /src && ./build.sh "$(cat VERSION)-custom"
Step 0 : RUN cd /src && ./build.sh "$(cat VERSION)-custom"
 ---> Running in b638c19089e1
fetch http://dl-4.alpinelinux.org/alpine/v3.1/main/x86_64/APKINDEX.tar.gz
(1/21) Installing go (1.3.3-r1)
(2/21) Installing run-parts (4.4-r0)
(3/21) Installing openssl (1.0.1m-r1)
(4/21) Installing lua5.2-libs (5.2.3-r0)
(5/21) Installing lua5.2 (5.2.3-r0)
(6/21) Installing lua5.2-posix (32-r1)
(7/21) Installing ca-certificates (20141019-r0)
(8/21) Installing libssh2 (1.4.3-r0)
(9/21) Installing curl (7.39.0-r0)
(10/21) Installing expat (2.1.0-r1)
(11/21) Installing pcre (8.36-r1)
(12/21) Installing git (2.2.1-r0)
(13/21) Installing libbz2 (1.0.6-r3)
(14/21) Installing libffi (3.0.13-r0)
(15/21) Installing gdbm (1.11-r0)
(16/21) Installing ncurses-terminfo-base (5.9-r3)
(17/21) Installing ncurses-libs (5.9-r3)
(18/21) Installing readline (6.3-r3)
(19/21) Installing sqlite-libs (3.8.7.4-r0)
(20/21) Installing python (2.7.9-r0)
(21/21) Installing mercurial (3.2.2-r0)
Executing busybox-1.22.1-r14.trigger
Executing ca-certificates-20141019-r0.trigger
OK: 173 MiB in 36 packages
(1/21) Purging go (1.3.3-r1)
(2/21) Purging git (2.2.1-r0)
(3/21) Purging mercurial (3.2.2-r0)
(4/21) Purging run-parts (4.4-r0)
(5/21) Purging openssl (1.0.1m-r1)
(6/21) Purging lua5.2-libs (5.2.3-r0)
(7/21) Purging lua5.2 (5.2.3-r0)
(8/21) Purging lua5.2-posix (32-r1)
(9/21) Purging ca-certificates (20141019-r0)
(10/21) Purging libssh2 (1.4.3-r0)
(11/21) Purging curl (7.39.0-r0)
(12/21) Purging expat (2.1.0-r1)
(13/21) Purging pcre (8.36-r1)
(14/21) Purging libbz2 (1.0.6-r3)
(15/21) Purging libffi (3.0.13-r0)
(16/21) Purging gdbm (1.11-r0)
(17/21) Purging ncurses-terminfo-base (5.9-r3)
(18/21) Purging ncurses-libs (5.9-r3)
(19/21) Purging readline (6.3-r3)
(20/21) Purging sqlite-libs (3.8.7.4-r0)
(21/21) Purging python (2.7.9-r0)
Executing busybox-1.22.1-r14.trigger
OK: 5 MiB in 15 packages
ln: /var/run/docker.sock: File exists
INFO[0093] The command [/bin/sh -c cd /src && ./build.sh "$(cat VERSION)-custom"] returned a non-zero code: 1