share: stop using 'islocal' with repo instance

Having this level of polymorphism of the `islocal` function is weird, and we
already have a way to know if the repo is local from the object itself.

We are about to deprecate passing a non-bytes object to `islocal`, so clean this
up beforehand.

We might want to clean up this function too in the future, however this is
another adventure.

mercurial/hg.py

@@ -299,8 +299,13 b' def share('
 ):
     '''create a shared repository'''
 
-    if not islocal(source):
-        raise error.Abort(_(b'can only share local repositories'))
+    not_local_msg = _(b'can only share local repositories')
+    if util.safehasattr(source, 'local'):
+        if source.local() is None:
+            raise error.Abort(not_local_msg)
+    elif not islocal(source):
+        # XXX why are we getting bytes here ?
+        raise error.Abort(not_local_msg)
 
     if not dest:
         dest = defaultdest(source)