pkg: Improve fetch error messages (#12490) #299

Job	Run time
Nix Build (ubuntu-latest)	5m 54s
Nix Build (macos-latest)	8m 48s
Nix Tests (ubuntu-latest)	23m 52s
Format	8m 33s
Documentation	1m 6s
Bootstrap (ubuntu-latest)	4m 23s
Cygwin Build	3m 7s
Nix Build 4.08 (ubuntu-latest)	5m 26s
Wasm_of_ocaml	7m 16s
Create local opam switch (macos-latest, 5)	13m 7s
Create local opam switch (ubuntu-latest, 5)	9m 13s
Coq 8.16.1	28m 38s
Build microbenchmarks	18m 19s
Build (5.3.x, ubuntu-latest, true)	9m 2s
Build (ocaml-variants.5.4.0+trunk, ubuntu-latest)	5m 18s
Build (5.3.x, macos-latest, true)	19m 42s
Build (5.3.x, macos-13)	16m 21s
Build (4.14.x, ubuntu-latest)	4m 21s
Build (ocaml-variants.4.14.2+options,ocaml-option-32bit, ubuntu-latest, true)	4m 38s
Build (4.14.x, macos-latest)	8m 14s
Build (ocaml-base-compiler.5.3.0,system-mingw, windows-latest, true)	21m 21s
Build (ocaml-compiler.5.3.0,system-msvc, windows-latest, true)	18m 3s
	4h 4m 42s

Provide feedback