Figure out the 'No SSL or TLS support compiled into Conduit' issue

Did not work:

cohttp                  4.1.2       An OCaml library for HTTP clients and servers
cohttp-lwt              4.1.2       CoHTTP implementation using the Lwt concurrency library
cohttp-lwt-unix         4.1.2       CoHTTP implementation for Unix and Windows using Lwt
conduit                 6.2.1       A network connection establishment library
conduit-lwt             6.2.1       A portable network connection establishment library using Lwt
conduit-lwt-unix        6.2.1       A network connection establishment library for Lwt_unix
tls                     0.17.4      Transport Layer Security purely in OCaml

Did not work (removed constraints):

$ opam list | grep 'cohttp\|conduit\|tls' 
cohttp                  5.3.1       An OCaml library for HTTP clients and servers
cohttp-lwt              5.3.0       CoHTTP implementation using the Lwt concurrency library
cohttp-lwt-unix         5.3.0       CoHTTP implementation for Unix and Windows using Lwt
conduit                 6.2.1       A network connection establishment library
conduit-lwt             6.2.1       A portable network connection establishment library using Lwt
conduit-lwt-unix        6.2.1       A network connection establishment library for Lwt_unix
tls                     0.17.4      Transport Layer Security purely in OCaml

Adding constraints:

  "tls" { < "1.33.0" }
  "cohttp-lwt-unix" { < "4.1.0" }

gives:

$ opam list | grep 'cohttp\|conduit\|tls'               
cohttp                  4.0.0       An OCaml library for HTTP clients and servers
cohttp-lwt              4.0.0       CoHTTP implementation using the Lwt concurrency library
cohttp-lwt-unix         4.0.0       CoHTTP implementation for Unix and Windows using Lwt
conduit                 4.0.2       A network connection establishment library
conduit-lwt             4.0.2       A portable network connection establishment library using Lwt
conduit-lwt-unix        4.0.2       A network connection establishment library for Lwt_unix
tls                     0.15.4      Transport Layer Security purely in OCaml

which works.