Merge branch 'maint-0.4.0' into maint-0.4.1

on_finish:

- ps: >-

    <# if we failed before install:, these functions won't be defined #>

    Function Execute-Command ($commandPath)

    {

        & $commandPath $args 2>&1

        if ( $LastExitCode -ne 0 ) {

            $host.SetShouldExit( $LastExitCode )

        }

    }

    Function Execute-Bash ()

    {

        Execute-Command 'c:\msys64\usr\bin\bash' '-e' '-c' $args

    }

    if ($env:compiler -eq "mingw") {

            <# use the MSYS2 user binaries to archive failures #>

            $oldpath = ${env:Path} -split ';'

  o Minor bugfixes (Appveyor CI):

    - Avoid spurious errors when Appveyor CI fails before the install step.

      Fixes bug 31884; bugfix on 0.3.4.2-alpha.