Fix unicode errors when changing to .format(...)

src/_pytest/_code/_py2traceback.py

@@ -2,7 +2,7 @@
 # CHANGES:
 # - some_str is replaced, trying to create unicode strings
 #
-from __future__ import absolute_import, division, print_function
+from __future__ import absolute_import, division, print_function, unicode_literals
 import types
 from six import text_type
 
@@ -51,17 +51,17 @@ def format_exception_only(etype, value):
         pass
     else:
         filename = filename or "<string>"
-        lines.append('  File "%s", line %d\n' % (filename, lineno))
+        lines.append('  File "{}", line {}\n'.format(filename, lineno))
         if badline is not None:
             if isinstance(badline, bytes):  # python 2 only
                 badline = badline.decode("utf-8", "replace")
-            lines.append(u"    %s\n" % badline.strip())
+            lines.append("    {}\n".format(badline.strip()))
             if offset is not None:
                 caretspace = badline.rstrip("\n")[:offset].lstrip()
                 # non-space whitespace (likes tabs) must be kept for alignment
                 caretspace = ((c.isspace() and c or " ") for c in caretspace)
                 # only three spaces to account for offset1 == pos 0
-                lines.append("   %s^\n" % "".join(caretspace))
+                lines.append("   {}^\n".format("".join(caretspace)))
         value = msg
 
     lines.append(_format_final_exc_line(stype, value))
@@ -72,9 +72,9 @@ def _format_final_exc_line(etype, value):
     """Return a list of a single line -- normal case for format_exception_only"""
     valuestr = _some_str(value)
     if value is None or not valuestr:
-        line = "%s\n" % etype
+        line = "{}\n".format(etype)
     else:
-        line = "%s: %s\n" % (etype, valuestr)
+        line = "{}: {}\n".format(etype, valuestr)
     return line
 
 
@@ -83,7 +83,7 @@ def _some_str(value):
         return text_type(value)
     except Exception:
         try:
-            return str(value)
+            return bytes(value).decode("UTF-8", "replace")
         except Exception:
             pass
-    return "<unprintable %s object>" % type(value).__name__
+    return "<unprintable {} object>".format(type(value).__name__)