Fix unpickling for python3

Turns out we can't use hasattr() since that triggers __getattr__() as well under python3 (but not python2). The note about this... "... it must do this by comparing the strings, rather than using hasattr or testing for an AttributeError." https://users.cs.cf.ac.uk/J.P.Giddy/python/gotcha/getattr.html

Fix unpickling for python3
d8e16b76 · Damian Johnson · 98d97717 · d8e16b76
Commit d8e16b76 authored May 18, 2015 by Damian Johnson
--- a/stem/descriptor/__init__.py
+++ b/stem/descriptor/__init__.py
@@ -594,9 +594,15 @@ class Descriptor(object):
    return stem.util.str_tools._to_unicode(digest_hash.hexdigest().upper())

  def __getattr__(self, name):
+    # Our constructor sets these, but when unpickling we might lack them. This
+    # check is needed to avoid an infinite loop in that case.
+
+    if name in ('_lazy_loading', 'ATTRIBUTES'):
+      return super(Descriptor, self).__getattribute__(name)
+
    # If attribute isn't already present we might be lazy loading it...

-    if hasattr(self, '_lazy_loading') and self._lazy_loading and name in self.ATTRIBUTES:
+    if self._lazy_loading and name in self.ATTRIBUTES:
      default, parsing_function = self.ATTRIBUTES[name]

      try: