chore: unnecessary use of fmt.Sprintf (#677)

Signed-off-by: guoguangwu <[email protected]>

Author: testwill

matchers/be_a_directory.go

@@ -52,5 +52,5 @@ func (matcher *BeADirectoryMatcher) FailureMessage(actual interface{}) (message
 }
 
 func (matcher *BeADirectoryMatcher) NegatedFailureMessage(actual interface{}) (message string) {
-	return format.Message(actual, fmt.Sprintf("not be a directory"))
+	return format.Message(actual, "not be a directory")
 }

matchers/be_a_regular_file.go

@@ -52,5 +52,5 @@ func (matcher *BeARegularFileMatcher) FailureMessage(actual interface{}) (messag
 }
 
 func (matcher *BeARegularFileMatcher) NegatedFailureMessage(actual interface{}) (message string) {
-	return format.Message(actual, fmt.Sprintf("not be a regular file"))
+	return format.Message(actual, "not be a regular file")
 }

matchers/be_an_existing_file.go

@@ -32,9 +32,9 @@ func (matcher *BeAnExistingFileMatcher) Match(actual interface{}) (success bool,
 }
 
 func (matcher *BeAnExistingFileMatcher) FailureMessage(actual interface{}) (message string) {
-	return format.Message(actual, fmt.Sprintf("to exist"))
+	return format.Message(actual, "to exist")
 }
 
 func (matcher *BeAnExistingFileMatcher) NegatedFailureMessage(actual interface{}) (message string) {
-	return format.Message(actual, fmt.Sprintf("not to exist"))
+	return format.Message(actual, "not to exist")
 }