differentiate paygen minios failure modes

Removed boolean return value from several functions where it was
unused.

BUG=b:268762826
TEST=recipes test train, try job

Change-Id: I8d1d9f5643d7a1ad89d9a224d7d1777fec06f5c6
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/4402549
Reviewed-by: Benjamin Shai <bshai@google.com>
Commit-Queue: Jack Neus <jackneus@google.com>
Tested-by: Jack Neus <jackneus@google.com>
Reviewed-by: Jae Hoon Kim <kimjae@chromium.org>
Reviewed-by: George Engelbrecht <engeg@google.com>
diff --git a/api/controller/payload.py b/api/controller/payload.py
index e713a84..3872cbc 100644
--- a/api/controller/payload.py
+++ b/api/controller/payload.py
@@ -120,8 +120,8 @@
         artifacts = payload_config.GeneratePayload()
     except paygen_payload_lib.PayloadGenerationSkippedException as e:
         # If paygen was skipped, provide a reason if possible.
-        if isinstance(e, paygen_payload_lib.NoMiniOSPartitionException):
-            reason = payload_pb2.GenerationResponse.NOT_MINIOS_COMPATIBLE
+        if isinstance(e, paygen_payload_lib.MiniOSException):
+            reason = e.return_code()
             output_proto.failure_reason = reason
 
     _SetGeneratePayloadOutputProto(output_proto, artifacts)