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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def add_fabfile():
 """ Copy the base fabfile.py to the current working directory. """

    fabfile_src  = os.path.join(PACKAGE_ROOT, 'fabfile.py')
    fabfile_dest = os.path.join(os.getcwd(), 'fabfile_deployer.py')

    if os.path.exists(fabfile_dest):
        print "`fabfile.py` exists in the current directory. " \
              "Please remove or rename it and try again."
        return

    shutil.copyfile(fabfile_src, fabfile_dest)