title: How to solve error installing PyObjC in Ubuntu 18.04
body: <p>I try to installing <code>PyObjC</code> using pip but still getting error</p>
  
  <blockquote>
    <p><code>ERROR: Command errored out with exit status 1:
         command: /usr/bin/python3.6 -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-819f93sh/pyobjc-framework-ScreenSaver/setup.py'"'"'; __file__='"'"'/tmp/pip-install-819f93sh/pyobjc-framework-ScreenSaver/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' egg_info --egg-base pip-egg-info
             cwd: /tmp/pip-install-819f93sh/pyobjc-framework-ScreenSaver/
        Complete output (15 lines):
        Traceback (most recent call last):
          File "&lt;string&gt;", line 1, in &lt;module&gt;
          File "/tmp/pip-install-819f93sh/pyobjc-framework-ScreenSaver/setup.py", line 21, in &lt;module&gt;
            extra_link_args=['-framework', 'ScreenSaver']),
          File "/tmp/pip-install-819f93sh/pyobjc-framework-ScreenSaver/pyobjc_setup.py", line 392, in Extension
            os_level = get_os_level()
          File "/tmp/pip-install-819f93sh/pyobjc-framework-ScreenSaver/pyobjc_setup.py", line 206, in get_os_level
            pl = plistlib.readPlist('/System/Library/CoreServices/SystemVersion.plist')
          File "/usr/lib/python3.6/plistlib.py", line 162, in readPlist
            with _maybe_open(pathOrFile, 'rb') as fp:
          File "/usr/lib/python3.6/contextlib.py", line 81, in __enter__
            return next(self.gen)
          File "/usr/lib/python3.6/plistlib.py", line 120, in _maybe_open
            with open(pathOrFile, mode) as fp:
        FileNotFoundError: [Errno 2] No such file or directory: '/System/Library/CoreServices/SystemVersion.plist'
        ----------------------------------------
    ERROR: Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.</code></p>
  </blockquote>