fix(deprecation): base64 encodestring is deprecated use encodebytes

https://docs.python.org/3.8/library/base64.html#base64.encodestring

encodestring is dropped in python3.9 (released today \o/)

--HG--
branch : 3.28

cubicweb/web/http_headers.py

@@ -1617,7 +1617,7 @@ generator_entity_headers = {
     'Content-Language': (generateList, singleHeader),
     'Content-Length': (unique, str, singleHeader),
     'Content-Location': (unique, str, singleHeader),
-    'Content-MD5': (base64.encodestring, lambda x: x.strip("\n"), singleHeader),
+    'Content-MD5': (base64.encodebytes, lambda x: x.strip("\n"), singleHeader),
     'Content-Range': (generateContentRange, singleHeader),
     'Content-Type': (generateContentType, singleHeader),
     'Expires': (generateDateTime, singleHeader),

cubicweb/web/test/unittest_application.py

@@ -640,7 +640,7 @@ class ApplicationTC(CubicWebTC):
         self.app.handle_request(req)
         self.assertEqual(401, req.status_out)
         clear_cache(req, 'get_authorization')
-        authstr = base64.encodestring(('%s:%s' % (self.admlogin, self.admpassword)).encode('ascii'))
+        authstr = base64.encodebytes(('%s:%s' % (self.admlogin, self.admpassword)).encode('ascii'))
         req.set_request_header('Authorization', 'basic %s' % authstr.decode('ascii'))
         self.assertAuthSuccess(req)
         req._url = 'logout'
@@ -717,10 +717,10 @@ class ApplicationTC(CubicWebTC):
     def test_http_auth_anon_allowed(self):
         req = self.init_authentication('http', 'anon')
         self._test_auth_anon(req)
-        authstr = base64.encodestring(b'toto:pouet')
+        authstr = base64.encodebytes(b'toto:pouet')
         req.set_request_header('Authorization', 'basic %s' % authstr.decode('ascii'))
         self._test_anon_auth_fail(req)
-        authstr = base64.encodestring(('%s:%s' % (self.admlogin, self.admpassword)).encode('ascii'))
+        authstr = base64.encodebytes(('%s:%s' % (self.admlogin, self.admpassword)).encode('ascii'))
         req.set_request_header('Authorization', 'basic %s' % authstr.decode('ascii'))
         self.assertAuthSuccess(req)
         req._url = 'logout'