Package source ID cannot be determined when the url can't be extrapolated for older version. (spack#14237)

Author: gartung

lib/spack/spack/package.py

@@ -1262,7 +1262,10 @@ def content_hash(self, content=None):
             raise spack.error.SpackError(err_msg)
 
         hash_content = list()
-        source_id = fs.for_package_version(self, self.version).source_id()
+        try:
+            source_id = fs.for_package_version(self, self.version).source_id()
+        except fs.ExtrapolationError:
+            source_id = None
         if not source_id:
             # TODO? in cases where a digest or source_id isn't available,
             # should this attempt to download the source and set one? This