docs: def build_pwm():
      """ Builds source with Python 2.7 and 3.2, and tests import """
      with cd("/tmp/source/c_pwm"):
          test = "import _PWM; print(_PWM.VERSION)"
          run("make py2.7")
          run('sudo python2.7 -c "%s"' % test)
          run("cp _PWM.so ../RPIO/PWM/")
          run("mv _PWM.so ../RPIO/PWM/_PWM27.so")
          run("make py3.2")
          run('python3.2 -c "%s"' % test)
          run("mv _PWM.so ../RPIO/PWM/_PWM32.so")