cmd/go: convert TestGoTestImportErrorStack to the script framework

The literal string match had to be turned into a regexp, otherwise
pretty straightforward.

Part of converting all tests to script framework to improve
test parallelism.

Updates #36320
Updates #17751

Change-Id: I46f62312f02dc9adf83ed91c6f807420d29fbb12
Reviewed-on: https://go-review.googlesource.com/c/go/+/212939
Run-TryBot: Michael Matloob <matloob@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>

src/cmd/go/go_test.go

@@ -3220,20 +3220,6 @@ func TestGoTestRaceFailures(t *testing.T) {
 	tg.grepBothNot("PASS", "something passed")
 }
 
-func TestGoTestImportErrorStack(t *testing.T) {
-	const out = `package testdep/p1 (test)
-	imports testdep/p2
-	imports testdep/p3: build constraints exclude all Go files `
-
-	tg := testgo(t)
-	defer tg.cleanup()
-	tg.setenv("GOPATH", filepath.Join(tg.pwd(), "testdata"))
-	tg.runFail("test", "testdep/p1")
-	if !strings.Contains(tg.stderr.String(), out) {
-		t.Fatalf("did not give full import stack:\n\n%s", tg.stderr.String())
-	}
-}
-
 func TestGoGetUpdate(t *testing.T) {
 	// golang.org/issue/9224.
 	// The recursive updating was trying to walk to

src/cmd/go/testdata/script/test_import_error_stack.txt

+! go test testdep/p1
+stderr 'package testdep/p1 \(test\)\n\timports testdep/p2\n\timports testdep/p3: build constraints exclude all Go files ' # check for full import stack
+
+-- testdep/p1/p1.go --
+package p1
+-- testdep/p1/p1_test.go --
+package p1
+
+import _ "testdep/p2"
+-- testdep/p2/p2.go --
+package p2
+
+import _ "testdep/p3"
+-- testdep/p3/p3.go --
+// +build ignore
+
+package ignored

src/cmd/go/testdata/src/testdep/p1/p1.go

-package p1

src/cmd/go/testdata/src/testdep/p1/p1_test.go

-package p1
-
-import _ "testdep/p2"

src/cmd/go/testdata/src/testdep/p2/p2.go

-package p2
-
-import _ "testdep/p3"

src/cmd/go/testdata/src/testdep/p3/p3.go

-// +build ignore
-
-package ignored