Create an enum for sender errors

Will replace usages of bools, and will now currently only be used
for indicating that messages were sent too fast

After we merge this commit we will replace this enum with a general
Status class for all of aos, similar to absl::Status.

Change-Id: I4b5b2e7685744b3c6826a241cd3c84190eaa96ee
Signed-off-by: milind-u <milind.upadhyay@gmail.com>
diff --git a/aos/network/message_bridge_test.cc b/aos/network/message_bridge_test.cc
index 2a43170..8246c22 100644
--- a/aos/network/message_bridge_test.cc
+++ b/aos/network/message_bridge_test.cc
@@ -450,7 +450,8 @@
       examples::Ping::Builder ping_builder =
           builder.MakeBuilder<examples::Ping>();
       ping_builder.add_value(ping_count + 971);
-      builder.Send(ping_builder.Finish());
+      EXPECT_EQ(builder.Send(ping_builder.Finish()),
+                RawSender::Error::kOk);
       ++ping_count;
     }
   });
@@ -985,7 +986,7 @@
   aos::Sender<examples::Ping>::Builder builder = sender->MakeBuilder();
   examples::Ping::Builder ping_builder = builder.MakeBuilder<examples::Ping>();
   ping_builder.add_value(value);
-  builder.Send(ping_builder.Finish());
+  builder.CheckOk(builder.Send(ping_builder.Finish()));
 }
 
 // Tests that when a message is sent before the bridge starts up, but is
@@ -1148,7 +1149,7 @@
     examples::Ping::Builder ping_builder =
         builder.MakeBuilder<examples::Ping>();
     ping_builder.add_value(1);
-    builder.Send(ping_builder.Finish());
+    builder.CheckOk(builder.Send(ping_builder.Finish()));
   }
 
   MakePi1Client();