MethodError: no method matching project_rel_path(::Pkg.Types.EnvCache, ::Nothing)

[ValentinKaisermayer]

Got this error as part of a docker build process using julia:1.11.4-bookworm

ERROR: MethodError: no method matching project_rel_path(::Pkg.Types.EnvCache, ::Nothing)
57.25 The function `project_rel_path` exists, but no method is defined for this combination of argument types.
57.55
57.55 Closest candidates are:
57.55   project_rel_path(::Pkg.Types.EnvCache, !Matched::String)
57.55    @ Pkg /usr/local/julia/share/julia/stdlib/v1.11/Pkg/src/Operations.jl:956
57.56
57.56 Stacktrace:
57.56   [1] package_info(env::Pkg.Types.EnvCache, pkg::Pkg.Types.PackageSpec, entry::Pkg.Types.PackageEntry)
57.56     @ Pkg.API /usr/local/julia/share/julia/stdlib/v1.11/Pkg/src/API.jl:66
57.56   [2] package_info
57.56     @ /usr/local/julia/share/julia/stdlib/v1.11/Pkg/src/API.jl:59 [inlined]
57.56   [3] #9
57.56     @ ./none:0 [inlined]
57.56   [4] iterate
57.56     @ ./generator.jl:48 [inlined]
57.56   [5] Dict{Base.UUID, Pkg.API.PackageInfo}(kv::Base.Generator{Vector{Pkg.Types.PackageSpec}, Pkg.API.var"#9#10"{Pkg.Types.EnvCache}})
57.67     @ Base ./dict.jl:95
57.67   [6] dict_with_eltype
57.67     @ ./abstractdict.jl:636 [inlined]
57.67   [7] dict_with_eltype
57.67     @ ./abstractdict.jl:643 [inlined]
57.67   [8] Dict
57.67     @ ./dict.jl:117 [inlined]
57.67   [9] dependencies
57.67     @ /usr/local/julia/share/julia/stdlib/v1.11/Pkg/src/API.jl:86 [inlined]
57.67  [10] dependencies()
57.67     @ Pkg.API /usr/local/julia/share/julia/stdlib/v1.11/Pkg/src/API.jl:83

I fixed it by changing the relative path of a local dependency:

[sources]
TestModule = {path = "../deps/TestModule"}

instead of

[sources]
TestModule = {path = "..\\deps\\TestModule"}

However, since I am on Windows Julia shows me paths (e.g. in tab-complete), e.g. like this:

julia> include("App\\test\\run
App\\test\\run.jl
App\\test\\runtests.jl