Only print file name in error messages

This will help with error deduplication.

git-svn-id: https://llvm.org/svn/llvm-project/zorg/trunk@324162 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/dep/dep.py b/dep/dep.py
index d19e021..e927d4c 100644
--- a/dep/dep.py
+++ b/dep/dep.py
@@ -26,6 +26,7 @@
 import re
 import subprocess
 
+import os
 
 try:
     # noinspection PyUnresolvedReferences
@@ -615,7 +616,7 @@
 
     def __repr__(self):
         """Reconstruct the line for pretty printing."""
-        return "{}:{}: {}{}".format(self.filename,
+        return "{}:{}: {}{}".format(os.path.basename(self.filename),
                                     self.line_number,
                                     self.text,
                                     " # " + self.comment if self.comment else "")