cascache.py: Update cache push/pull errors to be temporary

Further work needs to be done for the current grpc exceptions which are reraised.

buildstream/_artifactcache/cascache.py

@@ -340,7 +340,7 @@ class CASCache(ArtifactCache):
 
             except grpc.RpcError as e:
                 if e.code() != grpc.StatusCode.RESOURCE_EXHAUSTED:
-                    raise ArtifactError("Failed to push artifact {}: {}".format(refs, e)) from e
+                    raise ArtifactError("Failed to push artifact {}: {}".format(refs, e), temporary=True) from e
 
         return pushed
 

buildstream/_exceptions.py

@@ -254,8 +254,8 @@ class SandboxError(BstError):
 # Raised when errors are encountered in the artifact caches
 #
 class ArtifactError(BstError):
-    def __init__(self, message, *, detail=None, reason=None):
-        super().__init__(message, detail=detail, domain=ErrorDomain.ARTIFACT, reason=reason)
+    def __init__(self, message, *, detail=None, reason=None, temporary=False):
+        super().__init__(message, detail=detail, domain=ErrorDomain.ARTIFACT, reason=reason, temporary=True)
 
 
 # PipelineError