exchange: access requirements on repo instead of peer

As part of formalizing the peer interface, I audited for attribute
accesses for non-internal names to find API violations. This
uncovered the code changed in this commit.

localpeer.requirements is just an alias to the repo's requirements
attribute. So, change the code to get the data from the source
instead of relying on a one-off attribute in the localpeer type.

Differential Revision: https://phab.mercurial-scm.org/D265

mercurial/exchange.py

@@ -1226,8 +1226,10 b' def pull(repo, remote, heads=None, force'
         opargs = {}
     pullop = pulloperation(repo, remote, heads, force, bookmarks=bookmarks,
                            streamclonerequested=streamclonerequested, **opargs)
-    if pullop.remote.local():
-        missing = set(pullop.remote.requirements) - pullop.repo.supported
+
+    peerlocal = pullop.remote.local()
+    if peerlocal:
+        missing = set(peerlocal.requirements) - pullop.repo.supported
         if missing:
             msg = _("required features are not"
                     " supported in the destination:"