DeprecationWarning: make_current is deprecated

[hoxbro]

Seeing a lot of these warnings in the test suite.

  /usr/share/miniconda3/envs/test-environment/lib/python3.9/site-packages/tornado/ioloop.py:350: DeprecationWarning: make_current is deprecated; start the event loop first
    self.make_current()

[philippjfr]

This isn't our fault, Tornado added the deprecation but did not remove all calls to make_current from their codebase:

https://github.com/tornadoweb/tornado/blob/6cfa37ab4e03a7c82bfd2869ce528a452bd521e5/tornado/ioloop.py#L350

[hoxbro]

What about this one?

panel/panel/io/server.py

Line 875 in 4bcf011

loop.make_current()

[philippjfr]

Just spotted that too. Thanks!