Attempt revert before saving client (#232)

* Attempt revert before saving client

Attempting to avoid the following error which presents if a workspace has open files:

P4.P4Exception: [P4#run] Errors during command execution( "p4 client -i" )	
[Error]: "Client 'bk-p4-bk-95e7e0fc01359405a1a535adf3dbbc8135025a92-c5hk-1-midwinter' has files opened; use -f to force switch."

* Avoid infinite recursion

* catch case where no changes or client exist

* Print exceptions as warnings

python/perforce.py

@@ -124,6 +124,14 @@ def _setup_client(self):
         # unless overidden, overwrite writeable-but-unopened files
         # (e.g. interrupted syncs, artefacts that have been checked-in)
         client._options = self.client_options + ' clobber'
+
+        # revert changes in client before saving to avoid an error if files are still open in client
+        try:
+            self.perforce.run_revert('-w', '//...')
+        except P4Exception as ex:
+            # client might not exist yet, or not have any changes in either case that's fine
+            self.perforce.logger.warning("%s" % ex)
+            pass
 
         self.perforce.save_client(client)