initialize self.errors in run()

Initializing it to a (default)dict could cause problems if several
instances are used. We don't do that at the moment, but it's bad
practice to initialize class members to mutable data types which aren't
supposed to be shared between instances.

Signed-off-by: Nils Philippsen <nils@redhat.com>

distgit_bugzilla_sync/script.py

@@ -501,7 +501,6 @@ class DistgitBugzillaSync:
     _namespace_to_product = None
     _product_to_branch_regex = None
     _branch_regex_to_product = None
-    errors = collections.defaultdict(list)
 
     def send_email(self, from_address, to_address, subject, message, cc_address=None):
         '''Send an email if there's an error.
@@ -849,7 +848,7 @@ class DistgitBugzillaSync:
         self.env["print-no-change"] = self.args.print_no_change
 
         # Non-fatal errors to alert people about
-        errors = []
+        self.errors = collections.defaultdict(list)
 
         self.session = retry_session()