pw_protobuf_compiler: Nested oneof messages in repr

Cover nested messages in a oneof in the proto_repr() tests.

Change-Id: I6b687eb389cc7b6850209d99f8ff952b3dc0feae
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/96006
Reviewed-by: Alexei Frolov <frolv@google.com>
Pigweed-Auto-Submit: Wyatt Hepler <hepler@google.com>
Commit-Queue: Wyatt Hepler <hepler@google.com>

pw_protobuf_compiler/py/python_protos_test.py

@@ -267,7 +267,7 @@ def test_messages(self):
   oneof oneof_test {
     string oneof_1 = 15;
     int32 oneof_2 = 16;
-    float oneof_3 = 17;
+    Nested oneof_3 = 17;
   }
 
   map<string, Nested> mapping = 18;
@@ -363,8 +363,11 @@ def test_oneof(self):
                          "pw.test3.Message(oneof_1='test')")
         self.assertEqual(proto_repr(self.message(oneof_2=123)),
                          "pw.test3.Message(oneof_2=123)")
-        self.assertEqual(proto_repr(self.message(oneof_3=123)),
-                         "pw.test3.Message(oneof_3=123.0)")
+        self.assertEqual(
+            proto_repr(
+                self.message(oneof_3=self.nested(an_enum=self.enum.ONE))),
+            'pw.test3.Message('
+            'oneof_3=pw.test3.Nested(an_enum=pw.test3.Enum.ONE))')
 
         msg = self.message(oneof_1='test')
         msg.oneof_2 = 99