A file opened in 'b' mode needs bytes, not strings. Try to do this in a clean-ish way...

1 files changed, 2 insertions, 3 deletions

diff --git a/coverage/files.py b/coverage/files.py
index 9a8ac564..a68a0a7f 100644
--- a/coverage/files.py
+++ b/coverage/files.py
@@ -1,5 +1,6 @@
 """File wrangling."""
 
+from coverage.backward import to_string
 import fnmatch, os, sys
 
 class FileLocator(object):
@@ -72,9 +73,7 @@ class FileLocator(object):
                     data = zi.get_data(parts[1])
                 except IOError:
                     continue
-                if sys.version_info >= (3, 0):
-                    data = data.decode('utf8') # TODO: How to do this properly?
-                return data
+                return to_string(data)
         return None