Fix bug with printing error and warning messages with fmt verbs

cli/cli.go

@@ -37,7 +37,7 @@ import (
 // Application info
 const (
 	APP  = "bibop"
-	VER  = "4.8.0"
+	VER  = "4.8.1"
 	DESC = "Utility for testing command-line tools"
 )
 
@@ -312,12 +312,20 @@ func getRenderer() render.Renderer {
 
 // printError prints error message to console
 func printError(f string, a ...interface{}) {
-	fmtc.Fprintf(os.Stderr, "{r}"+f+"{!}\n", a...)
+	if len(a) == 0 {
+		fmtc.Fprintln(os.Stderr, "{r}"+f+"{!}")
+	} else {
+		fmtc.Fprintf(os.Stderr, "{r}"+f+"{!}\n", a...)
+	}
 }
 
 // printError prints warning message to console
 func printWarn(f string, a ...interface{}) {
-	fmtc.Fprintf(os.Stderr, "{y}"+f+"{!}\n", a...)
+	if len(a) == 0 {
+		fmtc.Fprintln(os.Stderr, "{y}"+f+"{!}")
+	} else {
+		fmtc.Fprintf(os.Stderr, "{y}"+f+"{!}\n", a...)
+	}
 }
 
 // printErrorAndExit print error mesage and exit with exit code 1