docs: def check_cmake_exists(cmake_command):
      """
      Check whether CMake is installed. If not, print
      informative error message and quits.
      """
      from subprocess import Popen, PIPE
  
      p = Popen(
          '{0} --version'.format(cmake_command),
          shell=True,
          stdin=PIPE,
          stdout=PIPE)
      if not ('cmake version' in p.communicate()[0].decode('UTF-8')):
          sys.stderr.write('   This code is built using CMake\n\n')
          sys.stderr.write('   CMake is not found\n')
          sys.stderr.write('   get CMake at http://www.cmake.org/\n')
          sys.stderr.write('   on many clusters CMake is installed\n')
          sys.stderr.write('   but you have to load it first:\n')
          sys.stderr.write('   $ module load cmake\n')
          sys.exit(1)