"<Package> not found in current path" during Pkg.build on recent master

[ararslan]

This seems to be happening both locally and on the nightly builds. As an example,

julia> Pkg.build("SpecialFunctions")
[ Info: Building SpecialFunctions
┌ Error: ------------------------------------------------------------
│ # Build failed for SpecialFunctions
│   exception =
│    LoadError: ArgumentError: Module Compat not found in current path.
│    Run `Pkg.add("Compat")` to install the Compat package.
│    Stacktrace:
│     [1] require(::Module, ::Symbol) at ./loading.jl:813
│     [2] include at ./boot.jl:292 [inlined]
│     [3] include_relative(::Module, ::String) at ./loading.jl:1011
│     [4] include at ./sysimg.jl:26 [inlined]
│     [5] include(::String) at ./loading.jl:1045
│     [6] top-level scope
│     [7] eval at ./boot.jl:295 [inlined]
│     [8] eval at ./sysimg.jl:71 [inlined]
│     [9] evalfile(::String, ::Array{String,1}) at ./loading.jl:1040 (repeats 2 times)
│     [10] #2 at ./none:12 [inlined]
│     [11] cd(::getfield(, Symbol("##2#5")){String}, ::String) at ./file.jl:70
│     [12] (::getfield(, Symbol("##1#3")))(::IOStream) at ./none:11
│     [13] open(::getfield(, Symbol("##1#3")), ::String, ::String) at ./iostream.jl:310
│     [14] top-level scope
│     [15] eval at ./boot.jl:295 [inlined]
│     [16] eval(::Module, ::Expr) at ./sysimg.jl:71
│     [17] process_options(::Base.JLOptions) at ./client.jl:301
│     [18] _start() at ./client.jl:375
│    in expression starting at /home/alex/.julia/v0.7/SpecialFunctions/deps/build.jl:1
└ @ Main none:15

Local version info:

Julia Version 0.7.0-DEV.3487
Commit 808e828* (2018-01-20 20:33 UTC)
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: Intel(R) Core(TM) i7-7700 CPU @ 3.60GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-3.9.1 (ORCJIT, skylake)
Environment:

Travis version info where I've also observed this:

Julia Version 0.7.0-DEV.3485
Commit a103ea3384 (2018-01-20 19:23 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: Intel(R) Xeon(R) CPU E5-2680 v2 @ 2.80GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-3.9.1 (ORCJIT, ivybridge)
Environment:

[quinnj]

Just saw this here too

[StefanKarpinski]

Could be related to the merging of #25455, although that passes all tests.

[chriselrod]

FWIW, I reproduced after Scott P Jones brought this up on gitter. Checking out the preceding commit #25649 fixed the issue.