Passing a parameter value with spaces in it seems to work but trigger an error #137

Because I am managing multiple levels of parameters ( some in shell, some in python, some for underlying system ), I need to pass a parameter like:

--params="value1 value2 value3".

Currently I get :
ERROR: Invalid remapping argument 'params=value1 value2 value3'

but this python code seems to work as expected :
@manager.option('-p', '--params', dest='params', default='')
def flask(params=''):
try:
app.logger.info('params%r', params)
#get params in list:
do_something(params.split()))

the logger gives me :
params u'value1 value2 value3'

Any idea why the ERROR ?