Delegated downloading of external files to Fuel. This hopefully fixes #71.

build.gradle

@@ -8,6 +8,7 @@ repositories {
 	maven { 
 		url "https://jitpack.io"
 	}
+	jcenter()
 }
 
 buildscript {
@@ -38,6 +39,7 @@ dependencies {
 	compile 'org.slf4j:slf4j-api:1.7.21'
 	compile 'ch.qos.logback:logback-classic:1.1.7'
 	compile 'com.google.code.gson:gson:2.5'
+	compile 'com.github.kittinunf.fuel:fuel:1.12.0'
 	
 	testCompile 'junit:junit:4.12'
 }

src/main/kotlin/de/fabianonline/telegram_backup/DownloadManager.kt

@@ -36,6 +36,9 @@ import com.github.badoualy.telegram.tl.api.request.TLRequestUploadGetFile
 import org.slf4j.LoggerFactory
 import org.slf4j.Logger
 import com.google.gson.Gson
+import com.github.kittinunf.fuel.Fuel
+import com.github.kittinunf.result.Result
+import com.github.kittinunf.result.getAs
 
 import java.io.IOException
 import java.io.File
@@ -502,8 +505,12 @@ class DownloadManager(internal var client: TelegramClient?, p: DownloadProgressI
 
 		@Throws(IOException::class)
 		fun downloadExternalFile(target: String, url: String): Boolean {
-			FileUtils.copyURLToFile(URL(url), File(target), 5000, 5000)
-			return true
+			val (_, response, result) = Fuel.get(url).response()
+			if (result is Result.Success) {
+				File(target).writeBytes(response.data)
+				return true
+			}
+			return false
 		}
 	}
 }