Get escaping issues working in all versions.

parso/python/normalizer.py

@@ -541,9 +541,16 @@ class ErrorFinder(Normalizer):
                     is_bytes = True
                 if 'u' in string_prefix:
                     is_bytes = False
-                func = codecs.escape_decode if is_bytes else codecs.unicode_escape_decode
+
+                payload = leaf._get_payload()
+                if is_bytes:
+                    payload = payload.encode('utf-8')
+                    func = codecs.escape_decode
+                else:
+                    func = codecs.unicode_escape_decode
+
                 try:
-                    func(leaf._get_payload())
+                    func(payload)
                 except UnicodeDecodeError as e:
                     self._add_syntax_error('(unicode error) ' + str(e), leaf)
                 except ValueError as e:

test/test_python_errors.py

@@ -306,6 +306,11 @@ def _get_actual_exception(code):
         except (SyntaxError, IndentationError) as e:
             wanted = e.__class__.__name__ + ': ' + e.msg
             line_nr = e.lineno
+        except ValueError as e:
+            # The ValueError comes from byte literals in Python 2 like '\x'
+            # that are oddly enough not SyntaxErrors.
+            wanted = 'SyntaxError: (value error) ' + str(e)
+            line_nr = None
         else:
             assert False, "The piece of code should raise an exception."