CVXPY >= 1.6.0 removes its dependency to ECOS

[cedricvincentcuaz]

Describe the bug

Current POT tests fail because of a change in dependencies of CVXPY (see updates here)

Screenshots

[cedricvincentcuaz]

Dear @eloitanguy,
Could you please try to fix this issue as you designed these solvers ?
Best regards,
Cédric