Traceback (most recent call last):

 "manage.py", line 116, in <module>
manager.run()

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/flask_script/__init__.py", line 423, in run
result = self.handle(sys.argv[0], sys.argv[1:])

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/flask_script/__init__.py", line 402, in handle
return handle(app, *positional_args, **kwargs)

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/flask_script/commands.py", line 145, in handle
return self.run(*args, **kwargs)

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/flask_migrate/__init__.py", line 107, in downgrade
command.downgrade(config, revision, sql = sql, tag = tag)

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/alembic/command.py", line 151, in downgrade
script.run_env()

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/alembic/script.py", line 203, in run_env
util.load_python_file(self.dir, 'env.py')

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/alembic/util.py", line 212, in load_python_file
module = load_module_py(module_id, path)

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/alembic/compat.py", line 58, in load_module_py
mod = imp.load_source(module_id, path, fp)

 "migrations/env.py", line 71, in <module>
run_migrations_online()

 "migrations/env.py", line 64, in run_migrations_online
context.run_migrations()

 "<string>", line 7, in run_migrations

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/alembic/environment.py", line 688, in run_migrations
self.get_context().run_migrations(**kw)

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/alembic/migration.py", line 258, in run_migrations
change(**kw)

 "migrations/versions/258d103c6224_mytable_slug.py", line 40, in downgrade
op.drop_constraint(None, 'mytable')

 "<string>", line 7, in drop_constraint

 "<string>", line 1, in <lambda>

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/alembic/util.py", line 329, in go
return fn(*arg, **kw)

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/alembic/operations.py", line 841, in drop_constraint
self.impl.drop_constraint(const)

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/alembic/ddl/impl.py", line 138, in drop_constraint
self._exec(schema.DropConstraint(const))

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/alembic/ddl/impl.py", line 76, in _exec
conn.execute(construct, *multiparams, **params)

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 729, in execute
return meth(self, multiparams, params)

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/sqlalchemy/sql/ddl.py", line 69, in _execute_on_connection
return connection._execute_ddl(self, multiparams, params)

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/sqlalchemy/engine/base.py", line 777, in _execute_ddl
compiled = ddl.compile(dialect=dialect)

 "<string>", line 1, in <lambda>

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/sqlalchemy/sql/elements.py", line 492, in compile
return self._compiler(dialect, bind=bind, **kw)

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/sqlalchemy/sql/ddl.py", line 27, in _compiler
return dialect.ddl_compiler(dialect, self, **kw)

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/sqlalchemy/sql/compiler.py", line 199, in __init__
self.string = self.process(self.statement, **compile_kwargs)

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/sqlalchemy/sql/compiler.py", line 222, in process
return obj._compiler_dispatch(self, **kwargs)

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/sqlalchemy/ext/compiler.py", line 413, in <lambda>
lambda *arg, **kw: existing(*arg, **kw))

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/sqlalchemy/ext/compiler.py", line 451, in __call__
return fn(element, compiler, **kw)

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/sqlalchemy/sql/visitors.py", line 80, in _compiler_dispatch
return meth(self, **kw)

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/sqlalchemy/sql/compiler.py", line 2518, in visit_drop_constraint
self.preparer.format_constraint(drop.element),

 "<string>", line 1, in <lambda>

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/sqlalchemy/sql/compiler.py", line 2928, in format_constraint
return self.quote(constraint.name)

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/sqlalchemy/sql/compiler.py", line 2893, in quote
if self._requires_quotes(ident):

 "/home/iurisilvio/.virtualenvs/fastshop/local/lib/python2.7/site-packages/sqlalchemy/sql/compiler.py", line 2864, in _requires_quotes
lc_value = value.lower()AttributeError: 'NoneType' object has no attribute 'lower'
E
execnet.gateway_base.RemoteError: Traceback (most recent call last):
E

 "x:\pytest-xdist\.env36\lib\site-packages\execnet\gateway_base.py", line 1076, in executetask
