tools: Add bright_red_output() to tools/lint-all

tools/lint-all

@@ -1,6 +1,7 @@
 #!/usr/bin/env python
 from __future__ import print_function
 from __future__ import absolute_import
+from contextlib import contextmanager
 import logging
 import os
 import re
@@ -11,7 +12,7 @@ import traceback
 
 try:
     import lister
-    from typing import cast, Any, Callable, Dict, List, Optional
+    from typing import cast, Any, Callable, Dict, List, Optional, Generator
 except ImportError as e:
     print("ImportError: {}".format(e))
     print("You need to run the Zulip linters inside a Zulip dev environment.")
@@ -36,6 +37,19 @@ zproject/settings.py
 zproject/test_settings.py
 """.split()
 
+@contextmanager
+def bright_red_output():
+    # type: () -> Generator[None, None, None]
+    # Make the lint output bright red
+    sys.stdout.write('\x1B[1;31m')
+    sys.stdout.flush()
+    try:
+        yield
+    finally:
+        # Restore normal terminal colors
+        sys.stdout.write('\x1B[0m')
+
+
 def check_pyflakes(options, by_lang):
     # type: (Any, Dict[str, List[str]]) -> bool
     if not by_lang['py']:
@@ -393,11 +407,7 @@ def run():
         lint_functions[func.__name__] = func
         return func
 
-    try:
-        # Make the lint output bright red
-        sys.stdout.write('\x1B[1;31m')
-        sys.stdout.flush()
-
+    with bright_red_output():
         @lint
         def templates():
             # type: () -> int
@@ -456,9 +466,5 @@ def run():
 
     sys.exit(1 if failed else 0)
 
-    finally:
-        # Restore normal terminal colors
-        sys.stdout.write('\x1B[0m')
-
 if __name__ == '__main__':
     run()