json: reject unicode on py2 as well

This makes it consistent with the behavior on py3.

Differential Revision: https://phab.mercurial-scm.org/D3536

mercurial/templatefilters.py

@@ -249,13 +249,9 b' def json(obj, paranoid=True):'
         return pycompat.bytestr(obj)
     elif isinstance(obj, bytes):
         return '"%s"' % encoding.jsonescape(obj, paranoid=paranoid)
-    elif isinstance(obj, str):
-        # This branch is unreachable on Python 2, because bytes == str
-        # and we'll return in the next-earlier block in the elif
-        # ladder. On Python 3, this helps us catch bugs before they
-        # hurt someone.
+    elif isinstance(obj, type(u'')):
         raise error.ProgrammingError(
-            'Mercurial only does output with bytes on Python 3: %r' % obj)
+            'Mercurial only does output with bytes: %r' % obj)
     elif util.safehasattr(obj, 'keys'):
         out = ['"%s": %s' % (encoding.jsonescape(k, paranoid=paranoid),
                              json(v, paranoid))