Artifact system swallows too many errors into a "failed to install error"

[KristofferC]

Right now, it feels like if you have any error in your Artifact file, Pkg will just say that it failed to install the artifact with no other explanation. For example, after manually calling stuff deeper and deeper I finally got:

julia> Pkg.PlatformEngines.download_verify_unpack("https://github.com/JuliaComputing/PackageCompilerX.jl/releases/download/v0.1/x86_64-8.1.0-release-posix-seh-rt_v6-rev0.tar.gz", "732f66bb9af48626dac6a694db275fa979748b59", "."; verbose=true)                                                   se-posix-se
[ Info: Downloading https://github.com/JuliaComputing/PackageCompilerX.jl/releases/download/v0.1/x86_64-8.1.0-release-posix-seh-rt_v6-rev0.tar.gz 
to C:\Users\KRISTO~1\AppData\Local\Temp\jl_7423.tmp-download.gz...                                                                                to C:\Users
ERROR: Hash must be 256 bits (64 characters) long, given hash is 40 characters long

instead of just

ERROR: Unable to automatically install 'x86_64-w64-mingw32' from 'C:\Users\Kristoffer\PackageCompilerX.jl\src\..\Artifacts.toml'

It would be good if we can say what actually get wrong.

[KristofferC]

Here is another case: https://discourse.julialang.org/t/problem-using-overrides-toml/34296

[maleadt]

Another case:

(@v1.5) pkg> add CompilerSupportLibraries_jll
  Resolving package versions...
ERROR: Unable to automatically install 'CompilerSupportLibraries' from '/home/pkgeval/.julia/packages/CompilerSupportLibraries_jll/790hI/Artifacts.toml'

Root cause, after hacking-in error reporting:

julia> Artifacts.download_artifact(Base.SHA1("76a62f5058af4a41326747a9e004fc4674c59dd1"), "https://github.com/JuliaBinaryWrappers/CompilerSupportLibraries_jll.jl/releases/download/CompilerSupportLibraries-v0.3.6+1/CompilerSupportLibraries.v0.3.6.x86_64-linux-gnu-libgfortran5.tar.gz")
ERROR: IOError: mktempdir: permission denied (EACCES)
Stacktrace:
 [1] uv_error at ./libuv.jl:97 [inlined]
 [2] mktempdir(::String; prefix::String, cleanup::Bool) at ./file.jl:665
 [3] mktempdir at ./file.jl:651 [inlined]
 [4] create_artifact(::Pkg.Artifacts.var"#50#51"{Bool,Bool,String,Nothing}) at /workspace/srcdir/usr/share/julia/stdlib/v1.5/Pkg/src/Artifacts.jl:210
 [5] download_artifact(::Base.SHA1, ::String, ::Nothing; verbose::Bool, quiet_download::Bool) at ./REPL[37]:46
 [6] download_artifact at ./REPL[37]:10 [inlined] (repeats 2 times)
 [7] top-level scope at REPL[38]:1