Consider unregistered if authorization fails.

This should only occur if another device has registered with the
same number, effectively making the current device unregistered.

library/src/org/whispersystems/textsecure/push/AuthorizationFailedException.java

@@ -0,0 +1,9 @@
+package org.whispersystems.textsecure.push;
+
+import java.io.IOException;
+
+public class AuthorizationFailedException extends IOException {
+  public AuthorizationFailedException(String s) {
+    super(s);
+  }
+}

library/src/org/whispersystems/textsecure/push/PushServiceSocket.java

@@ -269,6 +269,10 @@ public class PushServiceSocket {
       throw new RateLimitException("Rate limit exceeded: " + connection.getResponseCode());
     }
 
+    if (connection.getResponseCode() == 403) {
+      throw new AuthorizationFailedException("Authorization failed!");
+    }
+
     if (connection.getResponseCode() != 200) {
       throw new IOException("Bad response: " + connection.getResponseCode() + " " + connection.getResponseMessage());
     }

src/org/thoughtcrime/securesms/ApplicationPreferencesActivity.java

@@ -56,6 +56,7 @@ import org.thoughtcrime.securesms.util.MemoryCleaner;
 import org.thoughtcrime.securesms.util.TextSecurePreferences;
 import org.thoughtcrime.securesms.util.Trimmer;
 import org.thoughtcrime.securesms.util.Util;
+import org.whispersystems.textsecure.push.AuthorizationFailedException;
 import org.whispersystems.textsecure.push.PushServiceSocket;
 
 import java.io.IOException;
@@ -358,8 +359,11 @@ public class ApplicationPreferencesActivity extends PassphraseRequiredSherlockPr
               socket.unregisterGcmId();
               GCMRegistrar.unregister(context);
               return SUCCESS;
-            } catch (IOException e) {
-              Log.w("ApplicationPreferencesActivity", e);
+            } catch (AuthorizationFailedException afe) {
+              Log.w("ApplicationPreferencesActivity", afe);
+              return SUCCESS;
+            } catch (IOException ioe) {
+              Log.w("ApplicationPreferencesActivity", ioe);
               return NETWORK_ERROR;
             }
           }