restore ascii escaping for python 3.3/3.4

_pytest/compat.py

@@ -7,6 +7,7 @@ import inspect
 import types
 import re
 import functools
+import codecs
 
 import py
 
@@ -126,6 +127,19 @@ if _PY3:
     STRING_TYPES = bytes, str
     UNICODE_TYPES = str,
 
+    if PY35:
+        def _bytes_to_ascii(val):
+            return val.decode('ascii', 'backslashreplace')
+    else:
+        def _bytes_to_ascii(val):
+            if val:
+                # source: http://goo.gl/bGsnwC
+                encoded_bytes, _ = codecs.escape_encode(val)
+                return encoded_bytes.decode('ascii')
+            else:
+                # empty bytes crashes codecs.escape_encode (#1087)
+                return ''
+
     def _ascii_escaped(val):
         """If val is pure ascii, returns it as a str().  Otherwise, escapes
         bytes objects into a sequence of escaped bytes:
@@ -145,7 +159,7 @@ if _PY3:
 
         """
         if isinstance(val, bytes):
-            return val.decode('ascii', 'backslashreplace')
+            return _bytes_to_ascii(val)
         else:
             return val.encode('unicode_escape').decode('ascii')
 else: