[SSK] Better error messages when failing to send

// FREEBIE

Podfile.lock

@@ -134,7 +134,7 @@ EXTERNAL SOURCES:
 
 CHECKOUT OPTIONS:
   SignalServiceKit:
-    :commit: 3e10a49258dd825462af85e3efbc18676aa3e835
+    :commit: b6676fb029add0299f2cef0332058f5805d06ffa
     :git: https://github.com/WhisperSystems/SignalServiceKit.git
   SocketRocket:
     :commit: 41b57bb2fc292a814f758441a05243eb38457027

Signal/Signal-Info.plist

@@ -38,7 +38,7 @@
 		</dict>
 	</array>
 	<key>CFBundleVersion</key>
-	<string>2.6.3.7</string>
+	<string>2.6.3.8</string>
 	<key>ITSAppUsesNonExemptEncryption</key>
 	<false/>
 	<key>LOGS_EMAIL</key>