Pin astroid to fix tests
Pin astroid to fix tests

mitodl/XBlock,nagyistoce/edx-XBlock,nagyistoce/edx-XBlock,mitodl/XBlock,4eek/XBlock,edx-solutions/XBlock,edx-solutions/XBlock,4eek/XBlock,edx/XBlock,EDUlib/XBlock,EDUlib/XBlock,lovehhf/XBlock,edx/XBlock,lovehhf/XBlock