Add ansible-test units --num-workers option.

test/runner/lib/cli.py

@@ -382,6 +382,11 @@ def parse_args():
                        action='store_true',
                        help='collect tests but do not execute them')
 
+    # noinspection PyTypeChecker
+    units.add_argument('--num-workers',
+                       type=int,
+                       help='number of workers to use (default: auto)')
+
     units.add_argument('--requirements-mode',
                        choices=('only', 'skip'),
                        help=argparse.SUPPRESS)

test/runner/lib/config.py

@@ -261,6 +261,7 @@ class UnitsConfig(TestConfig):
         super(UnitsConfig, self).__init__(args, 'units')
 
         self.collect_only = args.collect_only  # type: bool
+        self.num_workers = args.num_workers  # type: int
 
         self.requirements_mode = args.requirements_mode if 'requirements_mode' in args else ''
 

test/runner/lib/executor.py

@@ -1331,7 +1331,7 @@ def command_units(args):
             'pytest',
             '--boxed',
             '-r', 'a',
-            '-n', 'auto',
+            '-n', str(args.num_workers) if args.num_workers else 'auto',
             '--color',
             'yes' if args.color else 'no',
             '--junit-xml',