Refactor to not check file existence, and open in only one place

mkdocs/config/base.py

@@ -156,29 +156,34 @@ def _open_config_file(config_file):
 
     # Default to the standard config filename.
     if config_file is None:
-        for possible_file_ending in ('yml', 'yaml'):
-            config_file = os.path.abspath('mkdocs.{}'.format(possible_file_ending))
-            if os.path.exists(config_file):
-                break
-        else:
-            config_file = os.path.abspath('mkdocs.yml')
-
-    # If closed file descriptor, get file path to reopen later.
-    if hasattr(config_file, 'closed') and config_file.closed:
-        config_file = config_file.name
-
-    log.debug(f"Loading configuration file: {config_file}")
-
+        paths_to_try = ['mkdocs.yml', 'mkdocs.yaml']
     # If it is a string, we can assume it is a path and attempt to open it.
-    if isinstance(config_file, str):
-        if os.path.exists(config_file):
-            config_file = open(config_file, 'rb')
+    elif isinstance(config_file, str):
+        paths_to_try = [config_file]
+    # If closed file descriptor, get file path to reopen later.
+    elif getattr(config_file, 'closed', False):
+        paths_to_try = [config_file.name]
+    else:
+        paths_to_try = None
+
+    if paths_to_try:
+        # config_file is not a file descriptor, so open it as a path.
+        for path in paths_to_try:
+            path = os.path.abspath(path)
+            log.debug(f"Loading configuration file: {path}")
+            try:
+                config_file = open(path, 'rb')
+                break
+            except FileNotFoundError:
+                continue
         else:
             raise exceptions.ConfigurationError(
-                f"Config file '{config_file}' does not exist.")
+                f"Config file '{paths_to_try[0]}' does not exist.")
+    else:
+        log.debug(f"Loading configuration file: {config_file}")
+        # Ensure file descriptor is at begining
+        config_file.seek(0)
 
-    # Ensure file descriptor is at begining
-    config_file.seek(0)
     try:
         yield config_file
     finally: