try to find heroku problem 🔧

migrations/env.py

@@ -23,8 +23,8 @@ logger = logging.getLogger('alembic.env')
 # target_metadata = mymodel.Base.metadata
 from flask import current_app
 config.set_main_option(
-    'sqlalchemy.url',
-    str(current_app.extensions['migrate'].db.engine.url).replace('%', '%%'))
+    'sqlalchemy.url', current_app.config.get(
+        'SQLALCHEMY_DATABASE_URI').replace('%', '%%'))
 target_metadata = current_app.extensions['migrate'].db.metadata
 
 # other values from the config, defined by the needs of env.py,
@@ -35,15 +35,12 @@ target_metadata = current_app.extensions['migrate'].db.metadata
 
 def run_migrations_offline():
     """Run migrations in 'offline' mode.
-
     This configures the context with just a URL
     and not an Engine, though an Engine is acceptable
     here as well.  By skipping the Engine creation
     we don't even need a DBAPI to be available.
-
     Calls to context.execute() here emit the given string to the
     script output.
-
     """
     url = config.get_main_option("sqlalchemy.url")
     context.configure(
@@ -56,10 +53,8 @@ def run_migrations_offline():
 
 def run_migrations_online():
     """Run migrations in 'online' mode.
-
     In this scenario we need to create an Engine
     and associate a connection with the context.
-
     """
 
     # this callback is used to prevent an auto-migration from being generated