bugfix: don't assume that status has status_code

[marado]

A 'twtxt following' call can fail with the following stack trace:

Traceback (most recent call last): File "/home/marado/.local/bin/twtxt", line 10, in sys.exit(main()) File "/home/marado/.local/lib/python3.7/site-packages/click/core.py", line 722, in call return self.main(args, kwargs) File "/home/marado/.local/lib/python3.7/site-packages/click/core.py", line 697, in main rv = self.invoke(ctx) File "/home/marado/.local/lib/python3.7/site-packages/click/core.py", line 1066, in invoke return _process_result(sub_ctx.command.invoke(sub_ctx)) File "/home/marado/.local/lib/python3.7/site-packages/click/core.py", line 895, in invoke return ctx.invoke(self.callback, ctx.params) File "/home/marado/.local/lib/python3.7/site-packages/click/core.py", line 535, in invoke return callback(args, *kwargs) File "/home/marado/.local/lib/python3.7/site-packages/click/decorators.py", line 17, in new_func return f(get_current_context(), args, **kwargs) File "/home/marado/.local/lib/python3.7/site-packages/twtxt/cli.py", line 218, in following click.echo(style_source_with_status(source, status, porcelain)) File "/home/marado/.local/lib/python3.7/site-packages/twtxt/helper.py", line 72, in style_source_with_status if status.status_code == 200: AttributeError: 'NoneType' object has no attribute 'status_code'

This happens because we're assuming that status has the property status_code, instead of validating first if that is the case. This patch fixes that.