Cypress crash : "TypeError: cannot read properties of undefined (reading 'message')"

[estellecomment]

Appeared during upgrade to 1.11.53 (#887)

All tests seem to crash on login.
Error is traced to cypress code itself, not our code, so don't know why.

I think a single test passed on Edge, once, and then stopped working. It could be a DB setup thing.

[estellecomment]

Logging by hand with same user works.
Reverting to develop_tchap pre-upgrade : cypress passes (headless)
Cypress version was not changed by upgrade.

[estellecomment]

Looks like a general slowdown is causing timeouts everywhere, including a timeout on theme load, hardcoded to 2s, which is causing the uncaught exception :
https://github.com/matrix-org/matrix-react-sdk/blob/cdfcd37b9426def8ef85269e5af6d47afbb3d1fe/src/theme.ts#L347

Extending all timeouts seems to help (defaultCommandTimeout: 20000, for cypress:open especially)
Since I'm running locally it's a bit hard to tell what's the cause. Change in the webpack command ? My machine ?