extensions: fix a debug message when searching for extensions

The "next" value was wrong. When 'hgext.NAME' is not found we now search for
'hgext3rd.NAME'.

mercurial/extensions.py

@@ -105,7 +105,7 b' def load(ui, name, path):'
         try:
             mod = _importh("hgext.%s" % name)
         except ImportError as err:
-            _reportimporterror(ui, err, "hgext.%s" % name, name)
+            _reportimporterror(ui, err, "hgext.%s" % name, "hgext3rd.%s" % name)
             try:
                 mod = _importh("hgext3rd.%s" % name)
             except ImportError as err:

tests/test-bad-extension.t

@@ -53,7 +53,7 b' show traceback for ImportError of hgext.'
   *** failed to import extension badext from $TESTTMP/badext.py: bit bucket overflow
   Traceback (most recent call last):
   Exception: bit bucket overflow
-  could not import hgext.badext2 (No module named *badext2): trying badext2 (glob)
+  could not import hgext.badext2 (No module named *badext2): trying hgext3rd.badext2 (glob)
   Traceback (most recent call last):
   ImportError: No module named *badext2 (glob)
   could not import hgext3rd.badext2 (No module named *badext2): trying badext2 (glob)