membership unit test checks joinability and player limit; post.create() checks allow_post

amanuensis/backend/membership.py

@@ -2,7 +2,6 @@
 Membership query interface
 """
 
-from _pytest.python_api import raises
 from sqlalchemy import select, func
 
 from amanuensis.db import DbContext, Membership
@@ -42,8 +41,7 @@ def create(
     lex: Lexicon = db(
         select(Lexicon).where(Lexicon.id == lexicon_id)
     ).scalar_one_or_none()
-    if not lex:
-        raise ArgumentError("could not find lexicon")
+    assert lex, "could not find lexicon"
 
     # Verify lexicon is joinable
     if not lex.joinable: