sqlalchemy: cant load plugin error

[rajat95]

I followed the steps as mentioned in the instructions but have run into the error the error mentioned in the heading. Please find the stacktrace below

Traceback (most recent call last):
File "manage.py", line 14, in
manager.run()
File "/home/rajat/.pyenv/versions/py3.6/lib/python3.6/site-packages/flask_script/init.py", line 417, in run
result = self.handle(argv[0], argv[1:])
File "/home/rajat/.pyenv/versions/py3.6/lib/python3.6/site-packages/flask_script/init.py", line 386, in handle
res = handle(*args, **config)
File "/home/rajat/.pyenv/versions/py3.6/lib/python3.6/site-packages/flask_script/commands.py", line 216, in call
return self.run(*args, **kwargs)
File "/home/rajat/.pyenv/versions/py3.6/lib/python3.6/site-packages/flask_migrate/init.py", line 95, in wrapped
f(*args, **kwargs)
File "/home/rajat/.pyenv/versions/py3.6/lib/python3.6/site-packages/flask_migrate/init.py", line 215, in migrate
version_path=version_path, rev_id=rev_id)
File "/home/rajat/.pyenv/versions/py3.6/lib/python3.6/site-packages/alembic/command.py", line 214, in revision
script_directory.run_env()
File "/home/rajat/.pyenv/versions/py3.6/lib/python3.6/site-packages/alembic/script/base.py", line 489, in run_env
util.load_python_file(self.dir, "env.py")
File "/home/rajat/.pyenv/versions/py3.6/lib/python3.6/site-packages/alembic/util/pyfiles.py", line 98, in load_python_file
module = load_module_py(module_id, path)
File "/home/rajat/.pyenv/versions/py3.6/lib/python3.6/site-packages/alembic/util/compat.py", line 173, in load_module_py
spec.loader.exec_module(module)
File "", line 678, in exec_module
File "", line 219, in _call_with_frames_removed
File "migrations/env.py", line 96, in
run_migrations_online()
File "migrations/env.py", line 78, in run_migrations_online
poolclass=pool.NullPool,
File "/home/rajat/.pyenv/versions/py3.6/lib/python3.6/site-packages/sqlalchemy/engine/init.py", line 499, in engine_from_config
return create_engine(url, **options)
File "/home/rajat/.pyenv/versions/py3.6/lib/python3.6/site-packages/sqlalchemy/engine/init.py", line 456, in create_engine
return strategy.create(*args, **kwargs)
File "/home/rajat/.pyenv/versions/py3.6/lib/python3.6/site-packages/sqlalchemy/engine/strategies.py", line 61, in create
entrypoint = u._get_entrypoint()
File "/home/rajat/.pyenv/versions/py3.6/lib/python3.6/site-packages/sqlalchemy/engine/url.py", line 172, in _get_entrypoint
cls = registry.load(name)
File "/home/rajat/.pyenv/versions/py3.6/lib/python3.6/site-packages/sqlalchemy/util/langhelpers.py", line 240, in load
"Can't load plugin: %s:%s" % (self.group, name)
sqlalchemy.exc.NoSuchModuleError: Can't load plugin: sqlalchemy.dialects:postgressql