[ERROR] The compilation of L2 failed at "make".
Processing 72/72: [L2: ocamlfind remove]
#=== ERROR while installing L2.1.0 ============================================#
# opam-version 1.2.2
# os           linux
# command      make
# path         /home/user/.opam/4.02.3/build/L2.1.0
# compiler     4.02.3
# exit-code    2
# env-file     /home/user/.opam/4.02.3/build/L2.1.0/L2-4058-aab1c6.env
# stdout-file  /home/user/.opam/4.02.3/build/L2.1.0/L2-4058-aab1c6.out
# stderr-file  /home/user/.opam/4.02.3/build/L2.1.0/L2-4058-aab1c6.err
### stdout ###
# [...]
# /home/user/.opam/system/bin/ocamlfind ocamldep -pp 'ppx-jane -dump-ast' -predicates ppx_driver -package yojson -package hashcons -package core_extended -package core -modules src/l2-lib/ast.ml > src/l2-lib/ast.ml.depends
# /home/user/.opam/system/bin/ocamlfind ocamldep -pp 'ppx-jane -dump-ast' -predicates ppx_driver -package yojson -package hashcons -package core_extended -package core -modules src/l2-lib/collections.ml > src/l2-lib/collections.ml.depends
# /home/user/.opam/system/bin/ocamlfind ocamldep -pp 'ppx-jane -dump-ast' -predicates ppx_driver -package yojson -package hashcons -package core_extended -package core -modules src/l2-lib/util.ml > src/l2-lib/util.ml.depends
# /home/user/.opam/system/bin/ocamlfind ocamlc -c -g -annot -bin-annot -thread -g -pp 'ppx-jane -dump-ast' -predicates ppx_driver -package yojson -package hashcons -package core_extended -package core -I src/l2-lib -o src/l2-lib/util.cmo src/l2-lib/util.ml
# + /home/user/.opam/system/bin/ocamlfind ocamlc -c -g -annot -bin-annot -thread -g -pp 'ppx-jane -dump-ast' -predicates ppx_driver -package yojson -package hashcons -package core_extended -package core -I src/l2-lib -o src/l2-lib/util.cmo src/l2-lib/util.ml
# File "src/l2-lib/util.ml", line 1:
# Error: /home/user/.opam/system/lib/core/core.cmi
# is not a compiled interface for this version of OCaml.
# It seems to be for an older version of OCaml.
# Command exited with code 2.
### stderr ###
# W: Cannot find source file matching module 'l2' in library l2.
# W: Use InterfacePatterns or ImplementationPatterns to define this file with feature "source_patterns".
# E: Failure("Command ''/usr/bin/ocamlbuild' src/l2-lib/l2.cma src/l2-lib/l2.cmxa src/l2-lib/l2.a src/l2-lib/l2.cmxs src/l2-cli/l2.native src/l2-cli/l2.byte src/l2-tests/tests.native -use-ocamlfind -j 8 -tag debug' terminated with error code 10")
# make: *** [build] Error 1



=-=- Error report -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
The following actions failed
  ∗  install L2 1.0
The following changes have been performed
  ∗  install   biniou        1.0.12
  ∗  install   conf-autoconf 0.1
  ∗  install   conf-which    1
  ∗  install   core          113.33.03
  ∗  install   core_extended 113.33.03
  ∗  install   core_kernel   113.33.03
  ∗  install   easy-format   1.2.0
  ∗  install   hashcons      1.2
  ∗  install   menhir        20151026
  ↘  downgrade ocamlfind     1.7.1 to 1.6.1
  ∗  install   ounit         2.0.0
  ∗  install   re2           113.33.03
  ∗  install   textutils     113.33.03
  ∗  install   yojson        1.3.3
[NOTE] Pinning command successful, but your installed packages may be out of sync.

The former state can be restored with:
    opam switch import "~/.opam/4.02.3/backup/state-20170006144414.export