templatespec: move check for non-unicode to lower-level function

Now that we have the factory functions, it makes sense to have the
check there.

Differential Revision: https://phab.mercurial-scm.org/D8847

mercurial/formatter.py

@@ -551,6 +551,8 b' def reference_templatespec(ref, refargs='
 
 
 def literal_templatespec(tmpl):
+    if pycompat.ispy3:
+        assert not isinstance(tmpl, str), b'tmpl must not be a str'
     return templatespec(b'', tmpl, None)
 
 

mercurial/logcmdutil.py

@@ -607,8 +607,6 b' def templatespec(tmpl, mapfile):'
     if mapfile:
         return formatter.mapfile_templatespec(b'changeset', mapfile)
     else:
-        if pycompat.ispy3:
-            assert not isinstance(tmpl, str), b'tmpl must not be a str'
         return formatter.literal_templatespec(tmpl)