fix flake8

steempy/account.py

steempy/asset.py

steempy/block.py

steempy/blockchainobject.py

steempy/exceptions.py

steempy/price.py

steempy/steem.py

steempy/transactionbuilder.py

steempy/utils.py

steempy/vote.py

steempy/wallet.py

steempyapi/steemnoderpc.py

steempybase/asset_permissions.py

steempybase/chains.py

steempybase/operations.py

tests/test_account.py

tests/test_base_objects.py

tests/test_message.py

tests/test_proposals.py

tests/test_steem.py