Handle non-deterministic __del__ in Repo

Fixes #610

Author: Byron

Diff for: git/repo/base.py

@@ -186,7 +186,10 @@ def __exit__(self, exc_type, exc_value, traceback):
         self.close()
 
     def __del__(self):
-        self.close()
+        try:
+            self.close()
+        except:
+            pass
 
     def close(self):
         if self.git: