Bug: Installing on MacOS through install.py

[Jordan-Pierce]

FYI, installing on MacOS throws an error at

        elif osused == 'Darwin':
            print('Trying to install gdal...')
            try:
                check_call(['brew', 'install', 'gdal'],
                        stdout=open(os.devnull, 'wb'), stderr=STDOUT)

and also

        out = subprocess.getstatusoutput(['cmake', '--version'])
        if out[0] != 0:
            if osused == 'Darwin':
                print('Trying to install cmake...')
                try:
                    check_call(['brew', 'install', 'cmake'],
                               stdout=open(os.devnull, 'wb'), stderr=STDOUT)
                except:
                    raise Exception('Impossible to install cmake through homebrew. Please install manually cmake before running '
                                    'this script.\nInstallation aborted.')

However, running the actual command from command line:

brew install gdal
brew install cmake

performs fine. Would help debugging, but I don't myself have a Mac.