extensions: preparatory refactoring

Small refactoring:

- use 'try..except' rather than 'if-then', which removes the need for a
  separate 'path' variable and is more 'pythonic'.
- promote log from 'debug' to 'info' and execute it immediately after
  loading before anything else.
- clarify comments related to INDEX_EXTENSIONS

kallithea/lib/utils.py

@@ -521,22 +521,23 b' def repo2db_mapper(initial_repo_dict, re'
 
 
 def load_extensions(root_path):
-    path = os.path.join(root_path, 'rcextensions', '__init__.py')
-    if os.path.isfile(path):
-        ext = create_module('rc', path)
+    try:
+        ext = create_module('rc', os.path.join(root_path, 'rcextensions', '__init__.py'))
+    except FileNotFoundError:
+        return
+
+    log.info('Loaded rcextensions from %s', ext)
         kallithea.EXTENSIONS = ext
-        log.debug('Found rcextensions now loading %s...', ext)
 
         # Additional mappings that are not present in the pygments lexers
         kallithea.config.conf.LANGUAGES_EXTENSIONS_MAP.update(getattr(ext, 'EXTRA_MAPPINGS', {}))
 
-        # OVERRIDE OUR EXTENSIONS FROM RC-EXTENSIONS (if present)
-
+    # Override any INDEX_EXTENSIONS
         if getattr(ext, 'INDEX_EXTENSIONS', []):
             log.debug('settings custom INDEX_EXTENSIONS')
             kallithea.config.conf.INDEX_EXTENSIONS = getattr(ext, 'INDEX_EXTENSIONS', [])
 
-        # ADDITIONAL MAPPINGS
+    # Additional INDEX_EXTENSIONS
         log.debug('adding extra into INDEX_EXTENSIONS')
         kallithea.config.conf.INDEX_EXTENSIONS.extend(getattr(ext, 'EXTRA_INDEX_EXTENSIONS', []))