ialagenchev@ialagenchev:~/mozilla-central/browser/devtools/webconsole/test$ ~/mozilla-central/mach mochitest-browser *875456*.js
Error running mach:

    ['mochitest-browser', 'browser_webconsole_bug_875456_mixedcontent_securityerrors.js']

The error occurred in code that was called by the mach command. This is either
a bug in the called code itself or in the way that mach is calling it.

You should consider filing a bug for this issue.

If filing a bug, please include the full output of mach, including this error
message.

The details of the failure are as follows:

AttributeError: 'NoneType' object has no attribute 'startswith'

  File "/Users/ialagenchev/mozilla-central/testing/mochitest/mach_commands.py", line 280, in run_mochitest_browser
    return self.run_mochitest(test_file, 'browser', **kwargs)
  File "/Users/ialagenchev/mozilla-central/testing/mochitest/mach_commands.py", line 299, in run_mochitest
    **kwargs)
  File "/Users/ialagenchev/mozilla-central/testing/mochitest/mach_commands.py", line 93, in run_mochitest_test
    ('.py', 'r', imp.PY_SOURCE))
  File "/Users/ialagenchev/mozilla-central/obj-x86_64-apple-darwin12.3.0/_tests/testing/mochitest/runtests.py", line 26, in <module>
    from mochitest_options import MochitestOptions
  File "/Users/ialagenchev/mozilla-central/obj-x86_64-apple-darwin12.3.0/_tests/testing/mochitest/mochitest_options.py", line 17, in <module>
    build_obj = MozbuildObject.from_environment()
  File "/Users/ialagenchev/mozilla-central/python/mozbuild/mozbuild/base.py", line 166, in from_environment
    topobjdir = os.path.normpath(config['topobjdir'] or topobjdir)
  File "/usr/local/Cellar/python/2.7.5/Frameworks/Python.framework/Versions/2.7/lib/python2.7/posixpath.py", line 327, in normpath
    initial_slashes = path.startswith('/')