UnboundLocalError: local variable 'element' referenced before assignment

[Mozejuice123]

self.ecb = sdmx.Request('ECB')
for currency in currencies:
key = dict(CURRENCY = currency, CURRENCY_DENOM = source_currency, FREQ='D', EXR_SUFFIX='A')**

Error happens here
** data = self.ecb.data('EXR',** key=key, params=parameters)

I get this output when running the code.
** local variable 'element' referenced before assignment
lxml.etree.XMLSyntaxError: no element found (line 0)