add some checks for whether exec cmd exits non-0 or output is blank

lib/readers/exec.go

@@ -18,6 +18,7 @@ package readers
 
 import (
 	"bytes"
+	"errors"
 	"os/exec"
 	"strings"
 )
@@ -36,6 +37,10 @@ func readExec(command string) (interface{}, error) {
 		return ExecInfo(""), err
 	}
 
+	if cmd.ProcessState.ExitCode() != 0 {
+		return ExecInfo(""), errors.New("returned non-zero exit code")
+	}
+
 	outputLines := strings.Split(stdout.String(), "\n")
 	if len(outputLines) == 0 {
 		return ExecInfo(""), nil

main.go

@@ -153,6 +153,9 @@ func main() {
 			mutex.Lock()
 			var combinedOutput string
 			for i, output := range moduleOutputs {
+				if output == "" {
+					continue
+				}
 				if i > 0 {
 					combinedOutput += delim
 				}