Python subprocess can't work more

Hi to All,
I need to test a package which comunicates with Odoo.
So I have to run Odoo in background, execute tests and then stop Odoo.
I used following statements to start/stop Odoo:
>>> prc = Process(target=run_odoo_cmd, args=(cmd_odoo,))
>>> prc.start()
[…] here test code […]
>>> prc.terminate()

Above test worked until July, 14th. After this date Odoo cannot start more, so test fails.

Is it changed something in travis environment?

Last failed test:

Last succesfull test:

In particular, in the raw log, I see an error about pip inable to upgrade some (presumably apt-installed) Python packages which ultimately results in an error about an incompatible version of one of them being present.

--ignore-installed is another problematic option: it is very likely to create a potentially broken configuration. Which is exactly what happened in your case.