Fix order of operations in readStderr

When go module outline linse are encountered they should be
printed to stderr, but not counted as errors.

Also remove error return when errHandler fails. We should
continue to record errors in the execution type.

testjson/execution.go

@@ -317,23 +317,19 @@ func readStderr(in io.Reader, handle errHandler, exec *Execution) chan error {
 		defer close(wait)
 		scanner := bufio.NewScanner(in)
 		for scanner.Scan() {
-			// TODO: remove this check if go module events stop being output as stdErr
-			if checkIsGoModuleEvent(scanner.Text()) {
+			line := scanner.Text()
+			handle(line)
+			if isGoModuleOutput(line) {
 				continue
 			}
-
-			exec.addError(scanner.Text())
-			if err := handle(scanner.Text()); err != nil {
-				wait <- err
-				return
-			}
+			exec.addError(line)
 		}
 		wait <- scanner.Err()
 	}()
 	return wait
 }
 
-func checkIsGoModuleEvent(scannerText string) bool {
+func isGoModuleOutput(scannerText string) bool {
 	prefixes := [2]string{"go: extracting", "go: downloading"}
 
 	for _, prefix := range prefixes {