opencc transition

Error log

The package failed to build. The error log from opam follows.

Opam plugin "depext" may require upgrading/reinstalling. Reinstall the plugin on the current switch? [Y/n] y
The following actions will be performed:
  - recompile opam-depext 1.2.3

<><> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><><><>
-> retrieved opam-depext.1.2.3  (cached)
-> removed   opam-depext.1.2.3
-> installed opam-depext.1.2.3
Done.

<><> opam-depext.1.2.3 installed successfully <><><><><><><><><><><><><><><><><>
=> opam-depext is unnecessary when used with opam >= 2.1. Please use opam install directly instead
# Run eval $(opam env) to update the current shell environment

<><> Carrying on to "opam depext -viy opencc.transition stdlib-shims.0.3.0 opencc1.1.0.1 integers.0.7.0 host-arch-x86_64.1 dune-configurator.3.16.0 dune.3.16.0 ctypes-foreign.0.23.0 ctypes.0.23.0 csexp.1.5.2 conf-pkg-config.3 conf-opencc1.1 conf-libffi.2.0.0 bigarray-compat.1.1.0" 

Since version 2.1, opam now handles external dependencies alongside OCaml ones, and the `depext` plugin interface is provided for backwards compatibility only. Consider using your usual `opam install` command to install both OCaml and system dependencies, or `opam install <pkg> --depext-only` if you want to only install external dependencies.
# Detecting depexts using vars: arch=x86_64, os=linux, os-distribution=debian, os-family=debian
[ERROR] No solution for opencc.transition & stdlib-shims.0.3.0 & opencc1.1.0.1 & integers.0.7.0 & host-arch-x86_64.1 & dune-configurator.3.16.0 & dune.3.16.0 & ctypes-foreign.0.23.0 & ctypes.0.23.0 & csexp.1.5.2 & conf-pkg-config.3 & conf-opencc1.1 & conf-libffi.2.0.0 & bigarray-compat.1.1.0:   * Missing dependency:
            - conf-opencc1
            depends on the unavailable system package 'libopencc2'. Use `--no-depexts' to attempt installation anyway, or it is possible that a depext package name in the opam file is incorrect.


Command failed: opam --cli=2.1 list --readonly --external '--resolve=opencc.transition,stdlib-shims.0.3.0,opencc1.1.0.1,integers.0.7.0,host-arch-x86_64.1,dune-configurator.3.16.0,dune.3.16.0,ctypes-foreign.0.23.0,ctypes.0.23.0,csexp.1.5.2,conf-pkg-config.3,conf-opencc1.1,conf-libffi.2.0.0,bigarray-compat.1.1.0' --color=never returned 20