Improved category slug collision test.

Fixed error message for unknown escape sequences.

nikola/nikola.py

@@ -1377,7 +1377,7 @@ def parse_category_name(self, category_name):
                         sys.exit(1)
                     esc_ch = category_name[next_backslash + 1]
                     if esc_ch not in {'/', '\\'}:
-                        utils.LOGGER.error("Unknown escape sequence '\\{0}' in '{1}' at last position!".format(esc_ch, category_name))
+                        utils.LOGGER.error("Unknown escape sequence '\\{0}' in '{1}'!".format(esc_ch, category_name))
                         sys.exit(1)
                     current += category_name[index:next_backslash] + esc_ch
                     index = next_backslash + 2

nikola/plugins/task/tags.py

@@ -107,12 +107,16 @@ def gen_tasks(self):
         categories = {}
         for category in self.site.posts_per_category.keys():
             slug = tuple(self.slugify_category_name(category))
+            for part in slug:
+                if len(part) == 0:
+                    utils.LOGGER.error("Category '{0}' yields invalid slug '{1}'!".format(category, '/'.join(slug)))
+                    sys.exit(1)
             if slug in categories:
                 other_category = categories[slug]
                 utils.LOGGER.error('You have categories that are too similar: {0} and {1}'.format(category, other_category))
                 utils.LOGGER.error('Category {0} is used in: {1}'.format(category, ', '.join([p.source_path for p in self.posts_per_category[category]])))
                 utils.LOGGER.error('Category {0} is used in: {1}'.format(other_category, ', '.join([p.source_path for p in self.posts_per_category[other_category]])))
-                pass
+                sys.exit(1)
             categories[slug] = category
 
         tag_list = list(self.site.posts_per_tag.items())