util: cli: FastChildWatcher windows incompatibility

Fixes: #485

Signed-off-by: John Andersen <[email protected]>

Author: pdxjohnny

CHANGELOG.md

@@ -21,6 +21,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   incorrectly.
 - `operations_parameter_set_pairs` moved to `MemoryOrchestratorContext`
 - Ignore generated files in `docs/plugins/`
+- Windows support by selecting `asyncio.ProactorEventLoop` and not using
+  `asyncio.FastChildWatcher`.
 
 ## [0.3.5] - 2020-03-10
 ### Added

dffml/util/cli/cmd.py

@@ -16,6 +16,9 @@
 
 DisplayHelp = "Display help message"
 
+if sys.platform == "win32":  # pragma: no cov
+    asyncio.set_event_loop(asyncio.ProactorEventLoop())
+
 
 class ParseLoggingAction(argparse.Action):
     def __call__(self, parser, namespace, value, option_string=None):
@@ -202,7 +205,11 @@ def main(cls, loop=None, argv=sys.argv):
             # is the default and may cause BlockingIOErrors when many
             # subprocesses are created
             # https://docs.python.org/3/library/asyncio-policy.html#asyncio.FastChildWatcher
-            if sys.version_info.major == 3 and sys.version_info.minor == 7:
+            if (
+                sys.version_info.major == 3
+                and sys.version_info.minor == 7
+                and sys.platform != "win32"
+            ):
                 watcher = asyncio.FastChildWatcher()
                 asyncio.set_child_watcher(watcher)
                 watcher.attach_loop(loop)