gpkit: Install permissions error

I was installing on OSX 10.11.5 and get the following permissions error. I got around this by running the commands with sudo, but seems like it might be worth looking into why this occurred. The permissions on ~/.gpkit/expopt.so were the same on my computer and Woody’s (but Woody doesn’t see this permissions error on his machine). My python version is 2.7.12 and my shutil is coming from '/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/shutil.pyc'

Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/private/var/folders/7d/1mt4zdqx4433fkghc5rxrc3h0000gn/T/pip-build-5vTY0r/gpkit/setup.py", line 9, in <module>
        build_gpkit()
      File "gpkit/build.py", line 299, in build_gpkit
        solvers = [CVXopt(), Mosek(), MosekCLI()]
      File "gpkit/build.py", line 90, in __init__
        self.installed = self.build()  # pylint: disable=not-callable
      File "gpkit/build.py", line 238, in build
        solib_dir = replacedir(pathjoin(os.path.expanduser("~"), ".gpkit"))
      File "gpkit/build.py", line 41, in replacedir
        shutil.rmtree(path)
      File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/shutil.py", line 252, in rmtree
        onerror(os.remove, fullname, sys.exc_info())
      File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/shutil.py", line 250, in rmtree
        os.remove(fullname)
    OSError: [Errno 13] Permission denied: '/Users/mayork/.gpkit/expopt.so'

    ----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in /private/var/folders/7d/1mt4zdqx4433fkghc5rxrc3h0000gn/T/pip-build-5vTY0r/gpkit/