'asynchronous' decorator not supported from Tornado 6.0

[benheartland]

https://github.com/moddevices/mod-sdk/blob/21a80729dde1439dcea03bfafbc42981fb503d8a/modsdk/webserver.py#L496

As noted in the release notes for Tornado 5.1.0 "The asynchronous decorator is deprecated and will be removed in 6.0." for tornado.web

Workaround: install Tornado 5.1.1 instead of the latest version (requires using pip rather than apt-get)

Output from running modsdk with Tornado 6.1 installed:

ben@207522396b28:/$ modsdk
Using raw lilv for plugin info (without checks)
Traceback (most recent call last):
  File "/usr/local/bin/modsdk", line 33, in <module>
    sys.exit(load_entry_point('modsdk==2.0.0', 'console_scripts', 'modsdk')())
  File "/usr/local/bin/modsdk", line 25, in importlib_load_entry_point
    return next(matches).load()
  File "/usr/lib/python3.9/importlib/metadata.py", line 77, in load
    module = import_module(match.group('module'))
  File "/usr/lib/python3.9/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1030, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
  File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 790, in exec_module
  File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
  File "/usr/local/lib/python3.9/dist-packages/modsdk/webserver.py", line 495, in <module>
    class Screenshot(JsonRequestHandler):
  File "/usr/local/lib/python3.9/dist-packages/modsdk/webserver.py", line 496, in Screenshot
    @web.asynchronous
AttributeError: module 'tornado.web' has no attribute 'asynchronous'

[brummer10]

#11
provide a patch to make it work with tornado > 5.1