New BaseFix class

my2to3/fixes/fix_division.py

 import __builtin__
 from collections import defaultdict
-import lib2to3.fixer_base
 import lib2to3.pgen2
 from lib2to3.pygram import python_symbols as syms
 from lib2to3.pytree import Leaf, Node
 import os
 import re
 
-from my2to3.util import add_future
+from my2to3.util import add_future, BaseFix
 
 trace_file_match = re.compile(r"^(.*)\|(.*)\|(.*) <type '(.*)'> / <type '(.*)'>$").match
 
@@ -47,7 +46,7 @@ def analyze_data(data):
   return False
 
 
-class FixDivision(lib2to3.fixer_base.BaseFix):
+class FixDivision(BaseFix):
   """Rewrites division_traced(n, a, b) into Py2/Py3-compatible division
 
   The `TRACE_FILE` environment variable must point to the trace data file. See

my2to3/fixes/fix_trace_division.py

 # https://lab.nexedi.com/nexedi/erp5/snippets/475
 from collections import defaultdict
-import lib2to3.fixer_base
 import lib2to3.fixer_util
 import lib2to3.pgen2
 from lib2to3.pygram import python_symbols as syms
 from lib2to3.pytree import Node
 import sys
 
+from my2to3.util import BaseFix
 
-class FixTraceDivision(lib2to3.fixer_base.BaseFix):
+
+class FixTraceDivision(BaseFix):
   """Rewrites a/b into division_traced(a, b)
 
   division_traced can be a function that looks up the stack and record the operand types, for example:

my2to3/util.py

 from lib2to3 import fixer_util
+import lib2to3.fixer_base
 from lib2to3.pytree import Leaf, Node
 from lib2to3.pgen2 import token
 from lib2to3.pygram import python_symbols as syms
+import os
+
+
+class BaseFix(lib2to3.fixer_base.BaseFix):
+  def start_tree(self, tree, filename):
+    sep = '-' * 5 # Arbitrary
+    if sep in filename:
+      filename = filename.split(sep, 1)[1].replace(sep, os.sep)
+
+    super(BaseFix, self).start_tree(tree, filename)
 
 
 # https://github.com/python-modernize/python-modernize/blob/84d973cb7b8153f9f7f22c3574a59312b2372ccb/libmodernize/__init__.py#L10-49