Removing virtualenv directory: /Users/palbrecht/dev/servo/python/_virtualenv
Error running mach:

    ['clean']

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:

Exception: Your system's gstreamer libraries are out of date (we need at least 1.12). If you're unable to install them, let us know by filing a bug!

  File "/Users/palbrecht/dev/servo/python/servo/build_commands.py", line 746, in clean
    env=self.build_env(), cwd=self.ports_servo_crate(), verbose=verbose)
  File "/Users/palbrecht/dev/servo/python/servo/command_base.py", line 612, in build_env
    if self.needs_gstreamer_env(target):
  File "/Users/palbrecht/dev/servo/python/servo/command_base.py", line 560, in needs_gstreamer_env
    install them, let us know by filing a bug!")