From the current state of ``registry``, create open_* functions

def make_open_functions():
    """From the current state of ``registry``, create open_* functions"""
    # Create shortcut open methods
    if hasattr(str, 'isidentifier'):
        def isidentifier(x):
            return x.isidentifier()
    else:
        IDENTIFIER_REGEX = re.compile(r'[a-zA-Z_][a-zA-Z0-9_]*$')
        isidentifier = IDENTIFIER_REGEX.match
    for plugin_name, plugin in registry.items():
        func_name = 'open_' + plugin_name
        if not isidentifier(func_name):
            # primitive name normalization
            func_name = re.sub('[-=~^&|@+]', '_', func_name)
        if isidentifier(func_name):
            globals()[func_name] = plugin
        else:
            warnings.warn('Invalid Intake plugin name "%s" found.' %
                          plugin_name)