Check for .blob attribute for astore

Author: jlwalke2

CHANGELOG.md

@@ -3,6 +3,7 @@ Unreleased
 ----------
 **Improvements**
 - Added `create_model_version` and `list_model_versions` to `model_repository`
+- Added an explicit `ValueError` when attempting to register an ASTORE that can't be downloaded.
 
 **Bugfixes**
 - Fixed an issue where `model_repository` did not find models by name once pagination limits were reached. 

src/sasctl/utils/astore.py

@@ -28,7 +28,12 @@ def create_package_from_astore(table):
     sess.loadactionset('astore')
 
     result = sess.astore.describe(rstore=table, epcode=True)
-    astore = sess.astore.download(rstore=table).blob
+    astore = sess.astore.download(rstore=table)
+    if not hasattr(astore, "blob"):
+        raise ValueError("Failed to download binary data for ASTORE '%s'."
+                         % astore)
+    astore = astore.blob
+
     astore = bytes(astore)      # Convert from SWAT blob type
 
     # Raise error if describe action fails