Ensure CLI doesn't panic when pulumi watch is used with policies enabled (#5569)

Fixes: #5561

CHANGELOG.md

@@ -2,7 +2,9 @@ CHANGELOG
 =========
 
 ## HEAD (Unreleased)
-_(none)_
+- [cli] Ensure that the CLI doesn't panic when using pulumi watch and policies are enabled
+  [#5569](https://github.com/pulumi/pulumi/pull/5569)
+
 
 ## 2.12.0 (2020-10-14)
 

pkg/backend/display/watch.go

@@ -50,6 +50,9 @@ func ShowWatchEvents(op string, action apitype.UpdateKind, events <-chan engine.
 		case engine.PreludeEvent, engine.SummaryEvent, engine.StdoutColorEvent:
 			// Ignore it
 			continue
+		case engine.PolicyViolationEvent:
+			// At this point in time, we don't handle policy events as part of pulumi watch
+			continue
 		case engine.DiagEvent:
 			// Skip any ephemeral or debug messages, and elide all colorization.
 			p := e.Payload().(engine.DiagEventPayload)