Fix TigerVNC detection for non-apt installations

[consideRatio]

I think we checked the case sensitive TigerVNC string which works if TigerVNC was installed via apt, but may not work when installed in another way. On the other hand, at those times, checking for the case insensitive string would work then. So, this PR makes the check case insensitive.

• Fixes TigerVNC check does not work for new versions of TigerVNC #69

Thank you @goekce for your thorough issue report!!

[github-actions]

👈 Launch a binder notebook on this branch for commit 2896efa

I will automatically update this comment whenever this PR is modified

[consideRatio]

Does this look right to you @goekce?

[yuvipanda]

LGTM if it works for the issue reporter!

[goekce]

I could not test on an installation due to lack of capacity right now.

I believe the command line arguments to tigervnc and turbovnc may be different. In #69 I had mentioned that -xstartup is not accepted by tigervnc:

jupyter-remote-desktop-proxy/jupyter_remote_desktop_proxy/__init__.py

Lines 34 to 35 in 024ab7d

	if not os.path.exists(os.path.expanduser('~/.vnc/xstartup')):
	vnc_args.extend(['-xstartup', os.path.join(HERE, 'share/xstartup')])

I searched for but could neither find any reference to xstartup in the source code of tigervnc nor in the documentation:

https://github.com/search?q=repo%3ATigerVNC%2Ftigervnc%20xstartup&type=code

Further arguments must also be tested:

jupyter-remote-desktop-proxy/jupyter_remote_desktop_proxy/__init__.py

Lines 37 to 46 in 024ab7d

	vnc_command = shlex.join(
	vnc_args
	+ [
	'-verbose',
	'-geometry',
	'1680x1050',
	'-SecurityTypes',
	'None',
	'-fg',
	]

This is the reason why I think in the long term the arguments should be configurable by the user.

[consideRatio]

Thank you @goekce, I opened #98 to represent that - let's go for a merge on this bug for now. I'll try to get it all the way so there is actual turbovnc support as we've commited to have.

[consideRatio]

Thank you for reviewing @yuvipanda and @goekce!!