This isolates logging from the standard library

This commit adds a custom encapsulated Logger, which then has its
methods exposed in a controlled fashion. This prevents external
libraries from modifying things such as the flags passed to the logger,
or where it should output to.

Change-Id: Ide4321246b1277fcee51608aa95532b8696b9777

pkg/log/log.go

@@ -3,46 +3,50 @@ package log
 import (
 	"io"
 	"log"
+	"os"
 )
 
-var debug = false
+var (
+	debug      = false
+	airshipLog = log.New(os.Stderr, "", log.LstdFlags)
+)
 
 // Init initializes settings related to logging
 func Init(debugFlag bool, out io.Writer) {
 	debug = debugFlag
-	log.SetOutput(out)
+	airshipLog.SetOutput(out)
 }
 
 // Debug is a wrapper for log.Debug
 func Debug(v ...interface{}) {
 	if debug {
-		log.Print(v...)
+		airshipLog.Print(v...)
 	}
 }
 
 // Debugf is a wrapper for log.Debugf
 func Debugf(format string, v ...interface{}) {
 	if debug {
-		log.Printf(format, v...)
+		airshipLog.Printf(format, v...)
 	}
 }
 
 // Print is a wrapper for log.Print
 func Print(v ...interface{}) {
-	log.Print(v...)
+	airshipLog.Print(v...)
 }
 
 // Printf is a wrapper for log.Printf
 func Printf(format string, v ...interface{}) {
-	log.Printf(format, v...)
+	airshipLog.Printf(format, v...)
 }
 
 // Fatal is a wrapper for log.Fatal
 func Fatal(v ...interface{}) {
-	log.Fatal(v...)
+	airshipLog.Fatal(v...)
 }
 
 // Fatalf is a wrapper for log.Fatalf
 func Fatalf(format string, v ...interface{}) {
-	log.Fatalf(format, v...)
+	airshipLog.Fatalf(format, v...)
 }