Fix redirect HTTP method handling (#3577)

Authored by: coletdjnz

yt_dlp/utils.py

@@ -1587,9 +1587,21 @@ def redirect_request(self, req, fp, code, msg, headers, newurl):
         CONTENT_HEADERS = ("content-length", "content-type")
         # NB: don't use dict comprehension for python 2.6 compatibility
         newheaders = {k: v for k, v in req.headers.items() if k.lower() not in CONTENT_HEADERS}
+
+        # A 303 must either use GET or HEAD for subsequent request
+        # https://datatracker.ietf.org/doc/html/rfc7231#section-6.4.4
+        if code == 303 and m != 'HEAD':
+            m = 'GET'
+        # 301 and 302 redirects are commonly turned into a GET from a POST
+        # for subsequent requests by browsers, so we'll do the same.
+        # https://datatracker.ietf.org/doc/html/rfc7231#section-6.4.2
+        # https://datatracker.ietf.org/doc/html/rfc7231#section-6.4.3
+        if code in (301, 302) and m == 'POST':
+            m = 'GET'
+
         return compat_urllib_request.Request(
             newurl, headers=newheaders, origin_req_host=req.origin_req_host,
-            unverifiable=True)
+            unverifiable=True, method=m)
 
 
 def extract_timezone(date_str):