Allow cylc lint to output error code if issues found

cylc/flow/scripts/lint.py

@@ -38,6 +38,7 @@
 from optparse import Values
 from pathlib import Path
 import re
+import sys
 import tomli
 from typing import Generator, Union
 
@@ -663,6 +664,13 @@ def get_option_parser() -> COP:
         metavar="CODE",
         choices=tuple([f'S{i["index"]:03d}' for i in STYLE_CHECKS.values()])
     )
+    parser.add_option(
+        '--error-on-issues', '-e',
+        help='Return an error code if any issues are raised.',
+        action='store_true',
+        default=False,
+        dest='error'
+    )
 
     return parser
 
@@ -759,6 +767,10 @@ def main(parser: COP, options: 'Values', target=None) -> None:
 
     print(msg)
 
+    # Exit with an error code if there were warnings if requested
+    if options.error and count > 0:
+        sys.exit(1)
+
 
 # NOTE: use += so that this works with __import__
 # (docstring needed for `cylc help all` output)