Fix unpickling FuncCode instances

This used to be an old-style class, and the pickle calls the OBJ opcode
(which for old-style classes creates an instance without calling __init__)
and later the BUILD opcode which calls __setstate__. Now that the class
is new-style, the OBJ opcode calls __init__, which breaks because the
pickle doesn't include args for __init__. So the workaround here is to
make __init__ accept no args (the object dict will still get set by the
subsequent BUILD op). Once the new-style object gets re-pickled it will
use the NEWOBJ opcode instead of OBJ, so unpickling will only call __new__
and not __init__.

src/Shared/DC/Scripts/Signature.py

@@ -21,8 +21,8 @@
 @total_ordering
 class FuncCode(object):
 
-    def __init__(self, varnames, argcount):
-        self.co_varnames = varnames
+    def __init__(self, varnames=None, argcount=0):
+        self.co_varnames = varnames or ()
         self.co_argcount = argcount
 
     def __eq__(self, other):