Fix to use flake8 bug -> use v3.9.2

Author: bjk7119

requirements-dev.txt

@@ -1,4 +1,5 @@
 tox
+flake8==3.9.2
 pytest
 pytest-cov
 pytest-flake8

src/fosslight_reuse/cli.py

@@ -21,13 +21,12 @@ def main():
     parser.add_argument('--help', '-h', help='Print help message', action='store_true', dest='help')
     try:
         args = parser.parse_args()
-    except:
+    except SystemExit:
         print_help_msg()
 
     if args.help:
         print_help_msg()
 
-
     if args.mode == "lint":
         run_lint(args.path, args.file, args.disable, args.output)
     elif args.mode == "report":