cascache.py: Raise ArtifactError on grpc errorQinusty/backport-576

This aims to fix issue #502.

1 files changed, 3 insertions, 1 deletions

diff --git a/buildstream/_artifactcache/cascache.py b/buildstream/_artifactcache/cascache.py
index 32de7d191..a8464c257 100644
--- a/buildstream/_artifactcache/cascache.py
+++ b/buildstream/_artifactcache/cascache.py
@@ -238,7 +238,8 @@ class CASCache(ArtifactCache):
 
             except grpc.RpcError as e:
                 if e.code() != grpc.StatusCode.NOT_FOUND:
-                    raise
+                    raise ArtifactError("Failed to pull artifact {}: {}".format(
+                        element._get_brief_display_key(), e)) from e
 
         return False
 
@@ -279,6 +280,7 @@ class CASCache(ArtifactCache):
 
                     except grpc.RpcError as e:
                         if e.code() != grpc.StatusCode.NOT_FOUND:
+                            # Intentionally re-raise RpcError for outer except block.
                             raise
 
                     missing_blobs = {}