check-code: do not prepend "warning" to a failure message

The prefix has not been removed when this check changed from a warning to a
failure.

contrib/check-code.py

@@ -216,7 +216,7 b' pypats = ['
     (r'(?i)descendent', "the proper spelling is descendAnt"),
     (r'\.debug\(\_', "don't mark debug messages for translation"),
     (r'\.strip\(\)\.split\(\)', "no need to strip before splitting"),
-    (r'^\s*except\s*:', "warning: naked except clause", r'#.*re-raises'),
+    (r'^\s*except\s*:', "naked except clause", r'#.*re-raises'),
     (r':\n(    )*( ){1,3}[^ ]', "must indent 4 spaces"),
     (r'ui\.(status|progress|write|note|warn)\([\'\"]x',
      "missing _() in ui message (use () to hide false-positives)"),

tests/test-check-code.t

@@ -163,13 +163,13 b''
    object comparison with literal
   [1]
 
-  $ cat > warning.py <<EOF
+  $ cat > for-nolineno.py <<EOF
   > except:
   > EOF
-  $ "$check_code" warning.py --warning --nolineno
-  warning.py:0:
+  $ "$check_code" for-nolineno.py --nolineno
+  for-nolineno.py:0:
    > except:
-   warning: naked except clause
+   naked except clause
   [1]
 
   $ cat > raise-format.py <<EOF