trace_division: append the caller's id to `division_traced`'s parameters

This id is a unique number that distinguishes callers from the same line.

my2to3/fixers/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
@@ -10,12 +11,13 @@ class FixTraceDivision(lib2to3.fixer_base.BaseFix):
 
   division_traced can be a function that looks up the stack and record the operand types, for example:
 
-      def division_traced(dividend, divisor):
+      def division_traced(id, dividend, divisor):
         import inspect
         previous_frame = inspect.currentframe().f_back
-        print ("{}:{} {} / {}".format(
+        print ("{}:{}:{} {} / {}".format(
             previous_frame.f_code.co_filename,
             previous_frame.f_lineno,
+            id,
             type(dividend),
             type(divisor)
         ))
@@ -25,6 +27,9 @@ class FixTraceDivision(lib2to3.fixer_base.BaseFix):
       __builtin__.division_traced = division_traced
 
   """
+  def start_tree(self, tree, filename):
+    super(FixTraceDivision, self).start_tree(tree, filename)
+    self.ids = defaultdict(int)
 
   def match(self, node):
     return (
@@ -32,12 +37,16 @@ class FixTraceDivision(lib2to3.fixer_base.BaseFix):
         node.children[1].type == lib2to3.pgen2.token.SLASH)
 
   def transform(self, node, results):
+    lineno = node.get_lineno()
     node.replace(
         lib2to3.fixer_util.Call(
             lib2to3.fixer_util.Name("division_traced"),
             args=(
+                lib2to3.fixer_util.Number(self.ids[lineno]),
+                lib2to3.fixer_util.Comma(),
                 node.children[0].clone(),
                 lib2to3.fixer_util.Comma(),
                 node.children[2].clone(),
             ),
             prefix=node.prefix))
+    self.ids[lineno] += 1