Fix RefreshTokenException('Could not find the Guest token in HTML')

ABOUT THE PROBLEM

This problem has recently begun to occur on some environments.
This doesn't happen every time, so if you are lucky, you don't get the
error.

The cause is literally literally that twint could not find the Guest
token in HTML.
Actually, sometimes token isn't included in HTML recently.

    #!/usr/bin/env python3
    # This program is WTFPL.
    import requests

res = requests.get('https://twitter.com')
print(res.text.split('\n')[-1])
twint require the result of running the above code is })();</script><script nonce="VALUE">document.cookie = decodeURIComponent("gt=VALUE; Max-Age=VALUE; Domain=.twitter.com; Path=/; Secure");</script>.
However, sometimes the result is only })();</script> and missing the
Guest token.

ABOUT THE SOLUTION

In this patch, twint get the Guest token from
https://api.twitter.com/1.1/guest/activate.json if could not find the
one.
The author referred to the code of gallery-dl:
https://github.com/mikf/gallery-dl/blob/47eae4c393f09937a5dbcc2cb978702fb173e747/gallery_dl/extractor/twitter.py#L780-L783

Author's note:

> I don't understand session of requests, so the code may be not good.
> I hope someone rewrite the patch better and create a pull request.

This commit was adopted from:
twintproject#1320 (comment)

Closes twintproject#1320.

twint/token.py

@@ -65,5 +65,30 @@ def refresh(self):
             logme.debug('Found guest token in HTML')
             self.config.Guest_token = str(match.group(1))
         else:
-            self.config.Guest_token = None
-            raise RefreshTokenException('Could not find the Guest token in HTML')
+            headers = {
+                'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Firefox/78.0',
+                'authority': 'api.twitter.com',
+                'content-length': '0',
+                'authorization': self.config.Bearer_token,
+                'x-twitter-client-language': 'en',
+                'x-csrf-token': res.cookies.get("ct0"),
+                'x-twitter-active-user': 'yes',
+                'content-type': 'application/x-www-form-urlencoded',
+                'accept': '*/*',
+                'sec-gpc': '1',
+                'origin': 'https://twitter.com',
+                'sec-fetch-site': 'same-site',
+                'sec-fetch-mode': 'cors',
+                'sec-fetch-dest': 'empty',
+                'referer': 'https://twitter.com/',
+                'accept-language': 'en-US',
+            }
+            self._session.headers.update(headers)
+            req = self._session.prepare_request(requests.Request('POST', 'https://api.twitter.com/1.1/guest/activate.json'))
+            res = self._session.send(req, allow_redirects=True, timeout=self._timeout)
+            match = re.search(r'{"guest_token":"(\d+)"}', res.text)
+            if match:
+                self.config.Guest_token = str(match.group(1))
+            else:
+                self.config.Guest_token = None
+                raise RefreshTokenException('Could not find the Guest token in HTML')