Warning from mach stage-build

scary-warning.err

alex@alex-ksquare:~/tor-browser$ ./mach build stage-package
/home/alex/tor-browser/testing/mozbase/mozsystemmonitor/mozsystemmonitor/resourcemonitor.py:266: UserWarning: psutil failed to run: not sure how to interpret line '   8       0 sda 381637 231217 14029637 296876 660191 2383224 84937712 1010416 0 456088 906520 35705 0 73009000 42258\n'
  warnings.warn('psutil failed to run: %s' % e)
 0:00.25 /usr/bin/make -j8 -s stage-package
 0:02.37 ../../dist/firefox/libplc4.so: No gain. Skipping
 0:02.37 ../../dist/firefox/libplds4.so: Couldn't find .bss. Skipping
 0:02.37 ../../dist/firefox/libmozgtk.so: Couldn't find .bss. Skipping
 0:02.38 ../../dist/firefox/gtk2/libmozgtk.so: Couldn't find .bss. Skipping
 0:02.38 ../../dist/firefox/libmozwayland.so: No gain. Skipping
 0:02.39 ../../dist/firefox/liblgpllibs.so: Couldn't find .bss. Skipping
 0:02.39 ../../dist/firefox/libnssdbm3.so: No gain. Skipping
 0:02.40 ../../dist/firefox/libsmime3.so: No gain. Skipping
 0:02.40 ../../dist/firefox/libsoftokn3.so: No gain. Skipping
 0:02.41 ../../dist/firefox/libmozsandbox.so: No gain. Skipping
 0:02.67 Wrote 438 files in 2332125 bytes to mozharness.zip in 0.16s
 0:02.72 258 compiler warnings present.
 0:02.75 Your build was successful!