fix(repo): prevent error messages from being swallowed

Byron · Byron · commit ec830a25d39d · 2016-06-13T09:03:13.000+02:00
This issue must have rosen from `to_progress_instance()` being inserted in a spot where `None` was a legit value. Fixes #462
diff --git a/git/repo/base.py b/git/repo/base.py
@@ -873,7 +873,8 @@ def init(cls, path=None, mkdir=True, odbt=DefaultDBType, **kwargs):
 
     @classmethod
     def _clone(cls, git, url, path, odb_default_type, progress, **kwargs):
-        progress = to_progress_instance(progress)
+        if progress is not None:
+            progress = to_progress_instance(progress)
 
         # special handling for windows for path at which the clone should be
         # created.
