Checking for available remotes: rsync and local, git, mercurial.
  - you won't be able to use darcs repositories unless you install the darcs command on your system.


=-=- Fetching repository information =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
[default] synchronized from https://opam.ocaml.org
[WARNING] External solver failed:
# opam-version 1.2.2
# os           linux
# command      aspcud /home/anthony/.opam/log/solver-in-12837-cc66ff /home/anthony/.opam/log/solver-out-12837-f802f4 -count(removed),-notuptodate(request),-sum(request,version-lag),-count(down),-notuptodate(changed),-count(changed),-notuptodate(solution),-sum(solution,version-lag)
# path         /home/anthony
# exit-code    1
# env-file     /home/anthony/.opam/log/log-12837-08473c.env
# stdout-file  /home/anthony/.opam/log/log-12837-08473c.out
# stderr-file  /home/anthony/.opam/log/log-12837-08473c.err
### stderr ###
# ERROR: grounder returned with non-zero exit status

[ERROR] External solver failure, please fix your installation and check /home/anthony/.opam/config and variable $OPAMEXTERNALSOLVER.
        You may also retry with option --use-internal-solver
[ERROR] Initialisation failed
OpamGlobals.Exit(66)