Windows doesn't like Unicode arguments to subprocess.Popen()

I'm actually surprised -- don't all the Win32 APIs have Unicode
versions?  Eh, Python.

Related to issue #23.

tests.py

@@ -706,6 +706,9 @@ def test_zest_releaser_check_failure_user_plods_on(self, check_manifest,
 class VCSHelper(object):
 
     def _run(self, *command):
+        # Windows doesn't like Unicode arguments to subprocess.Popen():
+        # https://github.com/mgedmin/check-manifest/issues/23#issuecomment-33933031
+        command = [s.encode(locale.getpreferredencoding()) for s in command]
         p = subprocess.Popen(command, stdout=subprocess.PIPE,
                              stderr=subprocess.STDOUT)
         stdout, stderr = p.communicate()