tools: Add a run() method to tools/lint-all.

tools/lint-all

@@ -7,6 +7,7 @@ import sys
 import optparse
 import subprocess
 import traceback
+
 try:
     import lister
     from typing import cast, Any, Callable, Dict, List, Optional
@@ -16,6 +17,8 @@ except ImportError as e:
     print("If you are using Vagrant, you can `vagrant ssh` to enter the Vagrant guest.")
     sys.exit(1)
 
+def run():
+    # type: () -> None
     parser = optparse.OptionParser()
     parser.add_option('--full',
         action='store_true',
@@ -456,3 +459,6 @@ try:
     finally:
         # Restore normal terminal colors
         sys.stdout.write('\x1B[0m')
+
+if __name__ == '__main__':
+    run()