Most of the tests fail with errors like this:

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ERROR: testGetClangOptionsForKnownCppFile (__main__.Chromium_ycmExtraConfTest)
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Traceback (most recent call last):
  File "tests/chromium.ycm_extra_conf_unittest.py", line 147, in testGetClangOptionsForKnownCppFile
    self.chrome_root, os.path.join(self.chrome_root, 'one.cpp'))
  File "chromium.ycm_extra_conf.py", line 323, in GetClangOptionsFromNinjaForFilename
    out_dir = os.path.realpath(GetNinjaOutputDirectory(chrome_root))
  File "/Users/sdy/lsrc/chromium/src/tools/vim/ninja_output.py", line 58, in GetNinjaOutputDirectory
    return max(generate_paths(), key=approx_directory_mtime)
  File "/Users/sdy/lsrc/chromium/src/tools/vim/ninja_output.py", line 47, in generate_paths
    for config in os.listdir(out_path):
OSError: [Errno 2] No such file or directory: '/var/folders/dl/slhx389x1k1bmnjh4hvjq3g000c2my/T/tmpYe_pj4/src/../../../../../../../private/var/folders/dl/slhx389x1k1bmnjh4hvjq3g000c2my/T/tmpYe_pj4/src/out'