Use KeyError.

Lib/cmp.py

@@ -34,7 +34,7 @@ def cmp(f1, f2): # Compare two files, use the cache if possible.
 			# cached signatures match
 			return outcome
 		# stale cached signature(s)
-	except RuntimeError:
+	except KeyError:
 		# cache miss
 		pass
 	# really compare

Lib/dircache.py

@@ -13,7 +13,7 @@ def listdir(path): # List directory contents, using cache
 	try:
 		cached_mtime, list = cache[path]
 		del cache[path]
-	except RuntimeError:
+	except KeyError:
 		cached_mtime, list = -1, []
 	try:
 		mtime = posix.stat(path)[8]