CocoaLumberjack Custom Crashlytics Logger in Swift

CrashlyticsLogger.swift

import Foundation
import CocoaLumberjack
import Crashlytics

class CrashlyticsLogger : DDAbstractLogger
{
    static let sharedInstance = CrashlyticsLogger()
    
    private var _logFormatter : DDLogFormatter?
    override var logFormatter: DDLogFormatter? {
        get {
            return _logFormatter
        }
        set {
            _logFormatter = newValue
        }
    }
    
    override func logMessage(logMessage: DDLogMessage)
    {
        guard let formatter = self.logFormatter
        else
        {
            print("CrashlyticsLogger: No formatter")
            return
        }
        
        let formattedMessage = formatter.formatLogMessage(logMessage)
        CLSLogv(formattedMessage, getVaList([]))
    }
}

CLSLogv is crashing if message contains % characters. formattedMessage.stringByRemovingPercentEncoding solves that issue

Removing or escaping the % signs isn't correct either. The Crashlytics docs say:

One important thing to note when using Swift is that the format argument of CLSLog, and NSLog, must be a compile-time constant string. While this is enforced by the compiler in Objective-C, it is currently lost in the bridging to Swift at the moment. A possible solution:

func write(string: String) {
   CLSLogv("%@", getVaList([string]))
}

Tried to implement this but am wondering where CustomLogFormatter() is defined?