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/project.py b/project.py
index 5a478b4..8212e0c 100755
--- a/project.py
+++ b/project.py
@@ -39,7 +39,7 @@
 from error import ManifestInvalidRevisionError
 from error import NoManifestException
 import platform_utils
-from trace import IsTrace, Trace
+from repo_trace import IsTrace, Trace
 
 from git_refs import GitRefs, HEAD, R_HEADS, R_TAGS, R_PUB, R_M