ocamlgraph 1.8.3

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 ocamlgraph.1.8.3 ocamlfind.1.9.6" <><><><>

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
# No extra OS packages requirements found.
[NOTE] Package ocamlfind is already installed (current version is 1.9.6).
The following actions will be performed:
  - install ocamlgraph 1.8.3

<><> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><><><>
Processing  1/3: [ocamlgraph.1.8.3: http]
Processing  1/3:
Processing  1/3: [ocamlgraph.1.8.3/install-findlib-dgraph.patch: dl]
-> retrieved ocamlgraph.1.8.3  (https://github.com/backtracking/ocamlgraph/releases/download/v1.8.3/ocamlgraph-1.8.3.tar.gz)
[ocamlgraph: patch] applying install-findlib-dgraph.patch
Processing  2/3: [ocamlgraph: patch]

#=== ERROR while compiling ocamlgraph.1.8.3 ===================================#
These patches didn't apply at /home/opam/.opam/4.05/.opam-switch/build/ocamlgraph.1.8.3:
  - install-findlib-dgraph.patch: "/usr/bin/patch -p1 -i /home/opam/.opam/log/processed-patch-115-867207" exited with code 1



<><> Error report <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
+- The following actions failed
| - build ocamlgraph 1.8.3
+- 
- No changes have been performed
# Run eval $(opam env) to update the current shell environment
'opam --cli=2.1 install ocamlgraph.1.8.3 ocamlfind.1.9.6 --verbose --yes --confirm-level=unsafe-yes' failed.