env: rm DB_ENGINE default value

Author: SomberNight

src/electrumx/server/env.py

@@ -224,8 +224,6 @@ def db_engine_enum(self) -> str:
         choices = list_db_engine_choices()
         db_eng = self.default('DB_ENGINE', None)
 
-        if db_eng is None and electrumx.__version__.startswith("1."):  # temporary legacy hack
-            db_eng = "leveldb"
         if db_eng is None:
             raise self.Error(
                 f"required envvar DB_ENGINE not set.\n"

tests/server/test_env.py

@@ -16,8 +16,9 @@
 
 base_environ = {
     'DB_DIRECTORY': BASE_DB_DIR,
+    'DB_ENGINE': 'rocksdb',
     'DAEMON_URL': BASE_DAEMON_URL,
-    'COIN': 'BitcoinSV',
+    'COIN': 'Bitcoin',
 }