run_recipe: add the ability to run yamllint over a recipe

This is a very rudimentary implementation and just runs yamllint in
a subprocess for a nicely colored and formatted output.

Right now this outputs a lot of indentation errors in the example
recipes, none of which are of consequence to the correctness of the
output.

run_recipe.py

@@ -5,6 +5,7 @@
 import os
 import shutil
 import argparse
+import subprocess
 import traceback
 import threading
 
@@ -282,6 +283,11 @@ def process_recipe(options):
 
     recipe = yaml.unsafe_load(f.read())
 
+    if options.lint_recipe:
+        # Just run yamllint in a subprocess for now. This also provides a nicely colored output.
+        subprocess.run(['yamllint', options.recipe])
+        exit()
+
     if options.dump_recipe or options.dump_recipe_only:
         output = dump(recipe, Dumper=Dumper)
         terminal_size = shutil.get_terminal_size()
@@ -365,6 +371,7 @@ def parse_arguments(arguments):
 
     parser.add_argument('--dump-recipe', action='store_true', default=False, help='Dump the loaded recipe; useful for finding errors in the recipe')
     parser.add_argument('--dump-recipe-only', action='store_true', default=False, help='Dump the loaded recipe and exit; useful for finding errors in the recipe')
+    parser.add_argument('--lint-recipe', action='store_true', default=False, help='Run yamllint over the specified recipe; useful for finding errors in the recipe')
 
     parser.add_argument('--debug', action='store_true', default=False, help='Enable debug mode. If an exception is encountered, drop into an ipdb debugger session')