headers = {
    'Content-Type': 'application/json;charset=UTF-8',
}

data = '{"currency":"USD"}'

import requests

response = requests.post('URL',
                         headers=headers, data=data)
print(response.text)
print(response.ok)
# Все работает, но переписатьна скрапи не могу 
# builtins.ValueError: not enough values to unpack (expected 2, got 1)

return scrapy.FormRequest(
    url='URL',
    method="POST",
    headers=headers,
    formdata=data,
    callback=self.after_check
)

class scrapy.http.Request(url[, callback, method='GET', headers, body, cookies, meta, encoding='utf-8', priority=0, dont_filter=False, errback, flags])

body (str or unicode) – the request body. If a unicode is passed, then it’s encoded to str using the encoding passed (which defaults to utf-8). If body is not given, an empty string is stored. Regardless of the type of this argument, the final value stored will be a str (never unicode or None).