Project file validation

[fredrikekre]

From JuliaLang/julia#37340 (comment)

julia> Pkg.update()
   Updating registry at `~/.julia/registries/General`
   Updating git-repo `https://github.com/fonsp/PlutoUtils.jl`
ERROR: Dependency `Test` in target `test` not listed in `deps` or `extras` section.

Stacktrace:
  [1] pkgerror(::String, ::Vararg{String, N} where N)
    @ Pkg.Types ~/julia-master/usr/share/julia/stdlib/v1.6/Pkg/src/Types.jl:52
  [2] validate(project::Pkg.Types.Project)
    @ Pkg.Types ~/julia-master/usr/share/julia/stdlib/v1.6/Pkg/src/project.jl:100
  [3] Pkg.Types.Project(raw::Dict{String, Any})
    @ Pkg.Types ~/julia-master/usr/share/julia/stdlib/v1.6/Pkg/src/project.jl:123
  [4] read_project(f_or_io::String)
    @ Pkg.Types ~/julia-master/usr/share/julia/stdlib/v1.6/Pkg/src/project.jl:136
  [5] read_package(path::String)
    @ Pkg.Types ~/julia-master/usr/share/julia/stdlib/v1.6/Pkg/src/Types.jl:403
  [6] deps_graph(ctx::Pkg.Types.Context, uuid_to_name::Dict{Base.UUID, String}, reqs::Dict{Base.UUID, Pkg.Types.VersionSpec}, fixed::Dict{Base.UUID, Pkg.Resolve.Fixed})
    @ Pkg.Operations ~/julia-master/usr/share/julia/stdlib/v1.6/Pkg/src/Operations.jl:441
  [7] resolve_versions!(ctx::Pkg.Types.Context, pkgs::Vector{Pkg.Types.PackageSpec})
    @ Pkg.Operations ~/julia-master/usr/share/julia/stdlib/v1.6/Pkg/src/Operations.jl:370
  [8] up(ctx::Pkg.Types.Context, pkgs::Vector{Pkg.Types.PackageSpec}, level::Pkg.Types.UpgradeLevel)
    @ Pkg.Operations ~/julia-master/usr/share/julia/stdlib/v1.6/Pkg/src/Operations.jl:1223
  [9] up(ctx::Pkg.Types.Context, pkgs::Vector{Pkg.Types.PackageSpec}; level::Pkg.Types.UpgradeLevel, mode::Pkg.Types.PackageMode, update_registry::Bool, kwargs::Base.Iterators.Pairs{Union{}, Union{}, Tuple{}, NamedTuple{(), Tuple{}}})
    @ Pkg.API ~/julia-master/usr/share/julia/stdlib/v1.6/Pkg/src/API.jl:245
 [10] up
    @ ~/julia-master/usr/share/julia/stdlib/v1.6/Pkg/src/API.jl:221 [inlined]
 [11] #up#38
    @ ~/julia-master/usr/share/julia/stdlib/v1.6/Pkg/src/API.jl:67 [inlined]
 [12] up
    @ ~/julia-master/usr/share/julia/stdlib/v1.6/Pkg/src/API.jl:67 [inlined]
 [13] up(; name::Nothing, uuid::Nothing, version::Nothing, url::Nothing, rev::Nothing, path::Nothing, mode::Pkg.Types.PackageMode, subdir::Nothing, kwargs::Base.Iterators.Pairs{Union{}, Union{}, Tuple{}, NamedTuple{(), Tuple{}}})
    @ Pkg.API ~/julia-master/usr/share/julia/stdlib/v1.6/Pkg/src/API.jl:80
 [14] up()
    @ Pkg.API ~/julia-master/usr/share/julia/stdlib/v1.6/Pkg/src/API.jl:72
 [15] top-level scope
    @ REPL[2]:1

Perhaps we don't have to be so strict and only error on Pkg.test here?