bui-manage db upgrade MySQL structure issue upon setup

I just installed burp and burp-ui over Ubuntu 16.04 AMD64 with MySQL 5.7.16. burp server is running.

bui-manage db upgrade gives the following error : sqlalchemy.exc.CompileError: (in table 'task', column 'uuid'): VARCHAR requires a length on dialect mysql

Full error log :

$ bui-manage db upgrade
INFO  [alembic.runtime.migration] Context impl MySQLImpl.
INFO  [alembic.runtime.migration] Will assume non-transactional DDL.
INFO  [alembic.runtime.migration] Running upgrade  -> 225d9b2f0fb1, initial
Traceback (most recent call last):
  File "/usr/local/bin/flask", line 11, in <module>
    sys.exit(main())
  File "/usr/local/lib/python2.7/dist-packages/flask/cli.py", line 478, in main
    cli.main(args=args, prog_name=name)
  File "/usr/local/lib/python2.7/dist-packages/flask/cli.py", line 345, in main
    return AppGroup.main(self, *args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 697, in main
    rv = self.invoke(ctx)
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 1066, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 1066, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 895, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 535, in invoke
    return callback(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/click/decorators.py", line 17, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/flask/cli.py", line 229, in decorator
    return __ctx.invoke(f, *args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 535, in invoke
    return callback(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/flask_migrate/cli.py", line 132, in upgrade
    _upgrade(directory, revision, sql, tag, x_arg)
  File "/usr/local/lib/python2.7/dist-packages/flask_migrate/__init__.py", line 242, in upgrade
    command.upgrade(config, revision, sql=sql, tag=tag)
  File "/usr/local/lib/python2.7/dist-packages/alembic/command.py", line 174, in upgrade
    script.run_env()
  File "/usr/local/lib/python2.7/dist-packages/alembic/script/base.py", line 416, in run_env
    util.load_python_file(self.dir, 'env.py')
  File "/usr/local/lib/python2.7/dist-packages/alembic/util/pyfiles.py", line 93, in load_python_file
    module = load_module_py(module_id, path)
  File "/usr/local/lib/python2.7/dist-packages/alembic/util/compat.py", line 79, in load_module_py
    mod = imp.load_source(module_id, path, fp)
  File "/usr/local/share/burpui/migrations/env.py", line 87, in <module>
    run_migrations_online()
  File "/usr/local/share/burpui/migrations/env.py", line 80, in run_migrations_online
    context.run_migrations()
  File "<string>", line 8, in run_migrations
  File "/usr/local/lib/python2.7/dist-packages/alembic/runtime/environment.py", line 797, in run_migrations
    self.get_context().run_migrations(**kw)
  File "/usr/local/lib/python2.7/dist-packages/alembic/runtime/migration.py", line 314, in run_migrations
    step.migration_fn(**kw)
  File "/usr/local/share/burpui/migrations/versions/225d9b2f0fb1_initial.py", line 27, in upgrade
    sa.UniqueConstraint('uuid')
  File "<string>", line 8, in create_table
  File "<string>", line 3, in create_table
  File "/usr/local/lib/python2.7/dist-packages/alembic/operations/ops.py", line 1098, in create_table
    return operations.invoke(op)
  File "/usr/local/lib/python2.7/dist-packages/alembic/operations/base.py", line 318, in invoke
    return fn(self, operation)
  File "/usr/local/lib/python2.7/dist-packages/alembic/operations/toimpl.py", line 101, in create_table
    operations.impl.create_table(table)
  File "/usr/local/lib/python2.7/dist-packages/alembic/ddl/impl.py", line 194, in create_table
    self._exec(schema.CreateTable(table))
  File "/usr/local/lib/python2.7/dist-packages/alembic/ddl/impl.py", line 118, in _exec
    return conn.execute(construct, *multiparams, **params)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 945, in execute
    return meth(self, multiparams, params)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/ddl.py", line 68, in _execute_on_connection
    return connection._execute_ddl(self, multiparams, params)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 996, in _execute_ddl
    if not self.schema_for_object.is_default else None)
  File "<string>", line 1, in <lambda>
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/elements.py", line 436, in compile
    return self._compiler(dialect, bind=bind, **kw)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/ddl.py", line 26, in _compiler
    return dialect.ddl_compiler(dialect, self, **kw)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 216, in __init__
    self.string = self.process(self.statement, **compile_kwargs)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 242, in process
    return obj._compiler_dispatch(self, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/visitors.py", line 81, in _compiler_dispatch
    return meth(self, **kw)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 2340, in visit_create_table
    (table.description, column.name, ce.args[0])
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/util/compat.py", line 202, in raise_from_cause
    reraise(type(exception), exception, tb=exc_tb, cause=cause)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 2329, in visit_create_table
    and not first_pk)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 242, in process
    return obj._compiler_dispatch(self, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/visitors.py", line 81, in _compiler_dispatch
    return meth(self, **kw)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 2360, in visit_create_column
    first_pk=first_pk
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/dialects/mysql/base.py", line 966, in get_column_specification
    column.type, type_expression=column)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 290, in process
    return type_._compiler_dispatch(self, **kw)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/visitors.py", line 81, in _compiler_dispatch
    return meth(self, **kw)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 2770, in visit_string
    return self.visit_VARCHAR(type_, **kw)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/dialects/mysql/base.py", line 1318, in visit_VARCHAR
    self.dialect.name)
sqlalchemy.exc.CompileError: (in table 'task', column 'uuid'): VARCHAR requires a length on dialect mysql