Fix acme.json file automatic creation

provider/acme/local_store_windows.go

@@ -0,0 +1,27 @@
+package acme
+
+import "os"
+
+// CheckFile checks file content size
+// Do not check file permissions on Windows right now
+func CheckFile(name string) (bool, error) {
+	f, err := os.Open(name)
+	if err != nil {
+		if os.IsNotExist(err) {
+			f, err = os.Create(name)
+			if err != nil {
+				return false, err
+			}
+			return false, f.Chmod(0600)
+		}
+		return false, err
+	}
+	defer f.Close()
+
+	fi, err := f.Stat()
+	if err != nil {
+		return false, err
+	}
+
+	return fi.Size() > 0, nil
+}