rename local trace module

There is a standard Python "trace" module, so having a local trace.py
prevents us being able to import that.  Rename the module to avoid.

Change-Id: I23e29ec95a2204bb168a641323d05e76968d9b57
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/234832
Reviewed-by: David Pursehouse <dpursehouse@collab.net>
Tested-by: Mike Frysinger <vapier@google.com>
diff --git a/git_command.py b/git_command.py
index f5352ea..6742303 100644
--- a/git_command.py
+++ b/git_command.py
@@ -23,7 +23,7 @@
 
 from error import GitError
 import platform_utils
-from trace import REPO_TRACE, IsTrace, Trace
+from repo_trace import REPO_TRACE, IsTrace, Trace
 from wrapper import Wrapper
 
 GIT = 'git'