config: return correct error

_conmonVersionFormatErr is a format string and it needs an error
argument.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

common/pkg/config/default.go

@@ -459,7 +459,7 @@ func probeConmon(conmonBinary string) error {
 
 	matches := r.FindStringSubmatch(out.String())
 	if len(matches) != 5 {
-		return errors.New(_conmonVersionFormatErr)
+		return fmt.Errorf(_conmonVersionFormatErr, errors.New("invalid version format"))
 	}
 	major, err := strconv.Atoi(matches[2])
 

common/pkg/config/default_test.go

@@ -1,6 +1,7 @@
 package config
 
 import (
+	"errors"
 	"fmt"
 	"io/ioutil"
 	"os"
@@ -57,7 +58,8 @@ func TestProbeConmon(t *testing.T) {
 			msg:    "failure invalid format",
 			output: "invalid",
 			assert: func(err error, msg string) {
-				assert.EqualError(t, err, _conmonVersionFormatErr, msg)
+				expectedErr := fmt.Errorf(_conmonVersionFormatErr, errors.New("invalid version format"))
+				assert.Equal(t, err, expectedErr, msg)
 			},
 		},
 	} {