fix errors

Author: antgonza

qiita_db/analysis.py

@@ -228,7 +228,7 @@ def delete_analysis_artifacts(cls, _id):
         aids = [a.id for a in analysis.artifacts if not a.parents]
         aids.sort(reverse=True)
         for aid in aids:
-            cls.delete(aid)
+            qdb.artifact.Artifact.delete(aid)
         cls.delete(analysis.id)
 
     @classmethod

qiita_ware/private_plugin.py

@@ -307,7 +307,7 @@ def delete_study(job):
 
         # deleting analyses
         for analysis in study.analyses():
-            qdb.analysis.Analysis.delete_analysis_artifacts(analysis)
+            qdb.analysis.Analysis.delete_analysis_artifacts(analysis.id)
 
         for pt in study.prep_templates():
             if pt.artifact is not None: