`pwd` might not exist causing errors when trying to print diagnostics

[KristofferC]

Saw this on Julia CI:

From worker 7:	┌ Error: JuliaSyntax parser failed — falling back to flisp!
--
  | From worker 7:	│   exception =
  | From worker 7:	│    IOError: pwd(): no such file or directory (ENOENT)
  | From worker 7:	│    Stacktrace:
  | From worker 7:	│      [1] uv_error
  | From worker 7:	│        @ Base ./libuv.jl:100 [inlined]
  | From worker 7:	│      [2] pwd()
  | From worker 7:	│        @ Base.Filesystem ./file.jl:63
  | From worker 7:	│      [3] abspath
  | From worker 7:	│        @ Base.Filesystem ./path.jl:431 [inlined]
  | From worker 7:	│      [4] _file_url(filename::String)
  | From worker 7:	│        @ Base.JuliaSyntax /cache/build/default-amdci5-3/julialang/julia-master/base/JuliaSyntax/src/diagnostics.jl:51
  | From worker 7:	│      [5] show_diagnostic(io::IOBuffer, diagnostic::Base.JuliaSyntax.Diagnostic, source::Base.JuliaSyntax.SourceFile)
  | From worker 7:	│        @ Base.JuliaSyntax /cache/build/default-amdci5-3/julialang/julia-master/base/JuliaSyntax/src/diagnostics.jl:68
  | From worker 7:	│      [6] show_diagnostics(io::IOBuffer, diagnostics::Vector{Base.JuliaSyntax.Diagnostic}, source::Base.JuliaSyntax.SourceFile)
  | From worker 7:	│        @ Base.JuliaSyntax /cache/build/default-amdci5-3/julialang/julia-master/base/JuliaSyntax/src/diagnostics.jl:86
  | From worker 7:	│      [7] showerror(io::IOBuffer, err::Base.JuliaSyntax.ParseError)