fix(storage): Avoid integration test segfaults. (googleapis#12419)

* fix(storage): Avoid integration test segfaults.

If the JWT private key file is not specified in an environment variable,
then skip the tests which would otherwise require it. This matches what
other tests do. Without this change, `jwt.Email` results in a nil
dereference.

* fix typo

* Move from skip to fatal

Author: cjc25

storage/integration_test.go

@@ -2682,7 +2682,7 @@ func TestIntegration_SignedURL(t *testing.T) {
 			t.Fatal(err)
 		}
 		if jwtConf == nil {
-			t.Skip("JSON key file is not present")
+			t.Fatal("JSON key file is not present")
 		}
 
 		bkt := client.Bucket(bucket)
@@ -2803,7 +2803,7 @@ func TestIntegration_SignedURL_WithEncryptionKeys(t *testing.T) {
 			t.Fatal(err)
 		}
 		if jwtConf == nil {
-			t.Skip("JSON key file is not present")
+			t.Fatal("JSON key file is not present")
 		}
 
 		bkt := client.Bucket(bucket)
@@ -2890,7 +2890,7 @@ func TestIntegration_SignedURL_EmptyStringObjectName(t *testing.T) {
 			t.Fatal(err)
 		}
 		if jwtConf == nil {
-			t.Skip("JSON key file is not present")
+			t.Fatal("JSON key file is not present")
 		}
 
 		opts := &SignedURLOptions{
@@ -4048,6 +4048,10 @@ func TestIntegration_RequesterPaysOwner(t *testing.T) {
 		if err != nil {
 			t.Fatalf("testutil.JWTConfig: %v", err)
 		}
+		if jwt == nil {
+			t.Fatal("JSON key file is not present")
+		}
+
 		// an account that has permissions on the project that owns the bucket
 		mainUserEmail := jwt.Email
 
@@ -6468,7 +6472,7 @@ func TestIntegration_PostPolicyV4(t *testing.T) {
 			t.Fatal(err)
 		}
 		if jwtConf == nil {
-			t.Skip("JSON key file is not present")
+			t.Fatal("JSON key file is not present")
 		}
 
 		projectID := testutil.ProjID()
@@ -6651,6 +6655,9 @@ func TestIntegration_SignedURL_DefaultSignBytes(t *testing.T) {
 		if err != nil {
 			t.Fatalf("unable to find test credentials: %v", err)
 		}
+		if jwt == nil {
+			t.Fatal("JSON key file is not present")
+		}
 
 		obj := "testBucketSignedURL"
 		contents := []byte("test")
@@ -6745,6 +6752,9 @@ func TestIntegration_PostPolicyV4_BucketDefault(t *testing.T) {
 		if err != nil {
 			t.Fatalf("unable to find test credentials: %v", err)
 		}
+		if jwt == nil {
+			t.Fatal("JSON key file is not present")
+		}
 
 		statusCodeToRespond := 200
 
@@ -6810,7 +6820,7 @@ func TestIntegration_PostPolicyV4_SignedURL_WithSignBytes(t *testing.T) {
 			t.Fatal(err)
 		}
 		if jwtConf == nil {
-			t.Skip("JSON key file is not present")
+			t.Fatal("JSON key file is not present")
 		}
 
 		signingFunc := func(b []byte) ([]byte, error) {