Clarify error using add_if_missing on ownerless asset (stac-utils#746)

* Clarify error using add_if_missing on ownerless asset * Add CHANGELOG entry for stac-utils#746
martinfleis · Feb 22, 2022 · 1a1ff77 · 1a1ff77
1 parent 94eb97c
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -17,6 +17,8 @@
 
 - Self links no longer included in Items for "relative published" catalogs ([#725](https://github.com/stac-utils/pystac/pull/725))
 - Adding New and Custom Extensions tutorial now up-to-date with new extensions API ([#724](https://github.com/stac-utils/pystac/pull/724))
+- Clarify error message when using `PropertyExtension.ext(..., add_if_missing=True)` on an `Asset`
+  with no owner([#746](https://github.com/stac-utils/pystac/pull/746))
 - Type errors when initializing `TemporalExtent` using a list of `datetime` objects ([#744](https://github.com/stac-utils/pystac/pull/744))
 
 ### Deprecated

diff --git a/pystac/extensions/base.py b/pystac/extensions/base.py
@@ -151,7 +151,8 @@ def validate_owner_has_extension(
         if asset.owner is None:
             if add_if_missing:
                 raise pystac.STACError(
-                    "Can only add schema URIs to Assets with an owner."
+                    "Attempted to use add_if_missing=True for an Asset with no owner. "
+                    "Use Asset.set_owner or set add_if_missing=False."
                 )
             else:
                 return