Change qrcode module import to be attempted only once.

import cStringIO

import logging

try:

    import qrcode

except ImportError:

    qrcode = False

    logging.warn("Could not import Python qrcode module.")

    logging.debug(("You'll need the qrcode Python module for this to "

                   "work. On Debian-based systems, this should be in the "

                   "python-qrcode package."))

def generateQR(bridgelines, imageFormat=u'JPEG'):

    """Generate a QRCode for the client's bridge lines.

    if not bridgelines:

        return

    if not qrcode:

        logging.info("Not creating QRCode for bridgelines; no qrcode module.")

    try:

        import qrcode

        qr = qrcode.QRCode()

        qr.add_data(bridgelines)

        return imgstr

    except ImportError as error:

        logging.error(str(error))

        logging.debug(("You'll need the qrcode Python module for this to "

                       "work. On Debian-based systems, this should be in the "

                       "python-qrcode package."))

    except KeyError as error:

        logging.error(str(error))

        logging.debug(("It seems python-imaging doesn't understand how to "