diff -r e4ccd7a69f77 -r a463f375f021 mercurial/httppeer.py
--- a/mercurial/httppeer.py	Thu Feb 01 19:32:42 2018 -0800
+++ b/mercurial/httppeer.py	Mon Feb 12 17:10:58 2018 -0800
@@ -221,13 +221,9 @@
     # Begin of _basewirepeer interface.
 
     def capabilities(self):
-        if self._caps is None:
-            try:
-                self._fetchcaps()
-            except error.RepoError:
-                self._caps = set()
-            self.ui.debug('capabilities: %s\n' %
-                          (' '.join(self._caps or ['none'])))
+        # self._fetchcaps() should have been called as part of peer
+        # handshake. So self._caps should always be set.
+        assert self._caps is not None
         return self._caps
 
     # End of _basewirepeer interface.