def path_reference_copy(copy_set, report=print):
    """
    Execute copying files of path_reference

    :arg copy_set: set of (from, to) pairs to copy.
    :type copy_set: set
    :arg report: function used for reporting warnings, takes a string argument.
    :type report: function
    """
    if not copy_set:
        return
    import os
    import shutil
    for file_src, file_dst in copy_set:
        if not os.path.exists(file_src):
            report('missing %r, not copying' % file_src)
        elif os.path.exists(file_dst) and os.path.samefile(file_src, file_dst):
            pass
        else:
            dir_to = os.path.dirname(file_dst)
            try:
                os.makedirs(dir_to, exist_ok=True)
            except:
                import traceback
                traceback.print_exc()
            try:
                shutil.copy(file_src, file_dst)
            except:
                import traceback
                traceback.print_exc()
