Support both import names of PyPI package python-multipart.

[renaudallard]

This allows synapse to run with python multipart >=0.0.13 without any tricky fallback. There is a conflict between 2 packages called multipart, so this should be modified.

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[reivilibre]

Requires Kludex/python-multipart#166 (0.0.13)

We support >=0.0.9:

synapse/pyproject.toml

Lines 228 to 229 in e80dad5

	# This is used for parsing multipart responses
	python-multipart = ">=0.0.9"

We either need to bump this version up (if it's OK with distro packagers) or support both versions for a while.

Given 0.0.13 was released on Oct 20, it seems a bit hard to ask distro packagers to update this dependency already, so I think supporting both import names would be prudent for now

[renaudallard]

Yes, perhaps it's safer to make a conditional import for the time being.

[arkamar]

Also, please, be aware of this twisted/treq#399, which basically ignited the python-multipart import name change. We already have to patch it locally in gentoo https://github.com/gentoo/gentoo/blob/cf6eec4024656661b7bf28da9576a50b0b579ff6/net-im/synapse/synapse-1.117.0-r1.ebuild#L182-L184 to deal with import collision for direct and indirect dependencies.

[renaudallard]

Also, please, be aware of this twisted/treq#399, which basically ignited the python-multipart import name change. We already have to patch it locally in gentoo https://github.com/gentoo/gentoo/blob/cf6eec4024656661b7bf28da9576a50b0b579ff6/net-im/synapse/synapse-1.117.0-r1.ebuild#L182-L184 to deal with import collision for direct and indirect dependencies.

This is exactly because of that conflict that I pushed the change in the first place. I am not completely sure how to solve the issue the cleanest possible way, but this clearly needs to be done upstream and not in package/ports systems.
On OpenBSD, www/py-multipart is already at 0.0.17 (in -current), but net/synapse package has not been patched in ports and still uses the old import name, but this is going to give issues at some point.

[reivilibre]

I added some changes to support both import names, supporting both <0.0.13 using the old name (for distro packagers who are still stuck on the old version, if any), and >=0.0.13 with the new name (to help avoid the name conflict).