Traceback (most recent call last):

 "toga_test.py", line 25, in <module>
app.main_loop()

 "/Users/santiagobasulto/.virtualenvs/toga/lib/python2.7/site-packages/toga_cocoa/app.py", line 103, in main_loop
self._startup()

 "/Users/santiagobasulto/.virtualenvs/toga/lib/python2.7/site-packages/toga_cocoa/app.py", line 92, in _startup
self.startup()

 "/Users/santiagobasulto/.virtualenvs/toga/lib/python2.7/site-packages/toga_cocoa/app.py", line 99, in startup
self.main_window.content = self._startup_method(self)

 "toga_test.py", line 15, in build
button.style.set(margin=50)AttributeError: 'Button' object has no attribute 'style'
Traceback (most recent call last):


 "src/gevent/greenlet.py", line 854, in gevent._greenlet.Greenlet.run


 "raiden/tasks.py", line 169, in _run


 "raiden/tasks.py", line 194, in loop_until_stop


 "raiden/network/rpc/client.py", line 913, in get_block


 "web3/eth.py", line 217, in getBlock


 "web3/manager.py", line 149, in request_blocking


 "web3/manager.py", line 128, in _make_request


 "web3/middleware/cache.py", line 134, in middleware


 "cytoolz/functoolz.pyx", line 250, in cytoolz.functoolz.curry.__call__


 "web3/middleware/formatting.py", line 75, in apply_formatters


 "web3/middleware/gas_price_strategy.py", line 34, in middleware


 "cytoolz/functoolz.pyx", line 250, in cytoolz.functoolz.curry.__call__


 "web3/middleware/formatting.py", line 75, in apply_formatters


 "web3/middleware/attrdict.py", line 33, in middleware


 "cytoolz/functoolz.pyx", line 250, in cytoolz.functoolz.curry.__call__


 "web3/middleware/formatting.py", line 73, in apply_formatters


 "web3/middleware/normalize_errors.py", line 25, in middleware


 "cytoolz/functoolz.pyx", line 250, in cytoolz.functoolz.curry.__call__


 "web3/middleware/formatting.py", line 75, in apply_formatters


 "cytoolz/functoolz.pyx", line 250, in cytoolz.functoolz.curry.__call__


 "web3/middleware/formatting.py", line 75, in apply_formatters


 "cytoolz/functoolz.pyx", line 250, in cytoolz.functoolz.curry.__call__


 "web3/middleware/formatting.py", line 75, in apply_formatters


 "web3/middleware/exception_retry_request.py", line 104, in middleware


 "web3/providers/rpc.py", line 85, in make_request


 "web3/providers/base.py", line 89, in decode_rpc_response


 "web3/_utils/encoding.py", line 223, in json_decode
json.decoder.JSONDecodeError: Could not decode '' because of Expecting value: line 1 column 1 (char 0).: line 1 column 1 (char 0)
