It seems like using .travis-docker.sh and opam2 it's not currently possible to build with ocaml verions older than 4.03.

I had a 4.02.3 build for key-parsers but there's no pre-installed 4.02 switch as part of the ocaml/opam2:debian-stable image as stated by the error:

Step 6/13 : RUN opam switch 4.02.3
 ---> Running in 7bf160a26fad
[ERROR] No switch 4.02.3 is currently installed. Did you mean 'opam switch create 4.02.3'?
        Installed switches are:
          - 4.07
          - 4.06
          - 4.05
          - 4.04
          - 4.03

Would it be possible to add such a switch? If not do you have any suggestions besides forcing opam 1.2.2?

Thanks!