oasis build fail

#=== ERROR while installing oasis.0.4.5 =======================================#
# opam-version 1.2.2
# os           linux
# command      ocaml setup.ml -install
# path         /home/bernardofpc/.opam/4.02.3/build/oasis.0.4.5
# compiler     4.02.3
# exit-code    1
# env-file     /home/bernardofpc/.opam/4.02.3/build/oasis.0.4.5/oasis-28891-52128c.env
# stdout-file  /home/bernardofpc/.opam/4.02.3/build/oasis.0.4.5/oasis-28891-52128c.out
# stderr-file  /home/bernardofpc/.opam/4.02.3/build/oasis.0.4.5/oasis-28891-52128c.err
### stderr ###
# File "src/oasis/OASISString.ml", line 148, characters 8-26:
# Warning 3: deprecated: String.set
# Use Bytes.set instead.
# File "src/oasis/OASISFindlib.ml", line 262, characters 6-24:
# Warning 3: deprecated: Lazy.lazy_from_fun
# Use Lazy.from_fun instead.
# ocamlfind: Package userconf is already installed
#  - (file /home/bernardofpc/.opam/4.02.3/lib/userconf/META already exists)
# E: Failure("Command ''/home/bernardofpc/.opam/4.02.3/bin/ocamlfind' install userconf src/ext/userconf/src/META _build/src/ext/userconf/src/UserConf.cmx _build/src/ext/userconf/src/UserConf.cmi _build/src/ext/userconf/src/userconf.cmxs _build/src/ext/userconf/src/userconf.a _build/src/ext/userconf/src/userconf.cmxa _build/src/ext/userconf/src/userconf.cma src/ext/userconf/src/UserConf.ml' terminated with error code 2")