list_ports() throws SP_ERR_MEM on Linux Arm64

[mgkuhn]

Any idea why the Travis CI checks fail for Linux Arm64 (e.g. in #74)?

$ julia --check-bounds=yes --color=yes -e "if VERSION < v\"0.7.0-DEV.5183\"; Pkg.test(\"${JL_PKG}\", coverage=true); else using Pkg; Pkg.test(coverage=true); end"
   Testing LibSerialPort
 Resolving package versions...
LibSerialPort CI port listing: Error During Test at /home/travis/build/JuliaIO/LibSerialPort.jl/test/runtests.jl:21
  Got exception outside of a @test
  libserialport returned SP_ERR_MEM - Memory allocation failed.
  Stacktrace:
   [1] error(::String) at ./error.jl:33
   [2] check(::SPReturn) at /home/travis/build/JuliaIO/LibSerialPort.jl/src/wrap.jl:299
   [3] #list_ports#3(::Int64, ::typeof(list_ports)) at /home/travis/build/JuliaIO/LibSerialPort.jl/src/wrap.jl:323
   [4] list_ports() at /home/travis/build/JuliaIO/LibSerialPort.jl/src/LibSerialPort.jl:280
   [5] top-level scope at /home/travis/build/JuliaIO/LibSerialPort.jl/test/runtests.jl:22

[samuelpowell]

Not yet but this has been the case for a while (it could have come in when we moved to the JLL build), so don't worry about this for your PR. We could do with checking this locally in case it is a CI issue.

[mgkuhn]

I would first have to get an Arm64 Linux system set up locally to investigate this problem, e.g. by installing Ubuntu Server on a Raspberry Pi 3 or newer.

[mgkuhn]

Since arm64 builds have long failed, I've edited in a recent commit to PR #74 the Travis config to allow arm64 to fail in Travis until that problem is fixed, such that PR authors for other issues do not get build errors that they are not responsible for.