* fix typo in pytest.mark.xskip
Change xskip by skipif marker as xskip is an unknown pytest marker.
* fix FileModeWarning
This fix the following warning:
FileModeWarning: Requests has determined the content-length for this request using the binary size of the file: however, the file has been opened in text mode (i.e. without the 'b' flag in the mode). This may lead to an incorrect content-length. In Requests 3.0, support will be removed for files in text mode.
* fix waring "calling yaml.load() without Loader=... is deprecated"
This fix the following warning:
YAMLLoadWarning: calling yaml.load() without Loader=... is deprecated, as the default Loader is unsafe. Please read https://msg.pyyaml.org/load for full details.
* fix collections.abc deprecation warning in python 3.7.
* update Flask dependency in order to get rid of the Request.is_xhr warning
This fix the following warning:
DeprecationWarning: 'Request.is_xhr' is deprecated as of version 0.13 and will be removed in version 1.0. The 'X-Requested-With' header is not standard and is unreliable. You may be able to use 'accept_mimetypes' instead.
