Fix two error messages.

slapos/recipe/cmmi/__init__.py

@@ -81,12 +81,12 @@ class Recipe(EnvironMixin):
         path = options.get('path')
         if url:
             if path:
-                raise UserError('You must provide either "url" or "path".')
+                raise UserError('You must use either "url" or "path", not both!')
             options['compile-directory'] = os.path.join(location, '.build')
         elif path:
             options['compile-directory'] = path
         else:
-            raise UserError('You must use either "url" or "path", not both!')
+            raise UserError('You must provide either "url" or "path".')
 
         for k, v in list(options.items()):
             if '@@LOCATION@@' in v: