Don't try decrypt values on community PRs

When a community member sends a pull request to the repo, travis can't
decrypt some environment variables which include decrypting the GCP
credentials.
In addition to this, there are a few tests that run that require the
`PULUMI_ACCESS_TOKEN` which can't be used.

This PR does 2 things:

- Adds a check to the GCP credentials decryption which checks the source
  of the PR (whether it's from within the local repo, or a fork)
- Sets an environment variable: `COMMUNITY_PRS` which is used downstream
  during some tests. If the var exists, some tests are skipped

This should enhance the experience for community pull requests
significantly

Fixes #4508

.travis.yml

@@ -15,8 +15,16 @@ sudo: true
 git:
   depth: false
 before_install:
-- openssl aes-256-cbc -K $encrypted_342342ee5e49_key -iv $encrypted_342342ee5e49_iv
-  -in gcp-credentials.json.enc -out gcp-credentials.json -d
+- |
+  if [ "$TRAVIS_PULL_REQUEST_SLUG" != "pulumi/pulumi" ]; 
+  then 
+    echo "Not decrypting gcp credentials";
+    export COMMUNITY_PR="true"
+  else 
+    echo "Decrypting gcp credentials"
+    openssl aes-256-cbc -K $encrypted_342342ee5e49_key -iv $encrypted_342342ee5e49_iv -in gcp-credentials.json.enc -out gcp-credentials.json -d
+    export COMMUNITY_PR="false"
+  fi
 - git clone https://github.com/pulumi/scripts ${GOPATH}/src/github.com/pulumi/scripts
 - source ${GOPATH}/src/github.com/pulumi/scripts/ci/prepare-environment.sh
 - source ${PULUMI_SCRIPTS}/ci/keep-failed-tests.sh

pkg/cmd/pulumi/new_test.go

@@ -807,6 +807,9 @@ func removeStack(t *testing.T, name string) {
 }
 
 func skipIfShort(t *testing.T) {
+	if os.Getenv("COMMUNITY_PR") == "true" {
+		t.Skip("Skipped for community PRs")
+	}
 	if testing.Short() {
 		t.Skip("Skipped in short test run")
 	}

pkg/npm/npm_test.go

@@ -33,6 +33,10 @@ func TestYarnInstall(t *testing.T) {
 }
 
 func testInstall(t *testing.T, expectedBin string) {
+	// Skip for community PRs
+	if os.Getenv("COMMUNITY_PR") == "true" {
+		t.Skip("Skipped for community PRs")
+	}
 	// Skip during short test runs since this test involves downloading dependencies.
 	if testing.Short() {
 		t.Skip("Skipped in short test run")