[Win32] Fix missing certs for HTTPS requests

The following error occured on Windows when switching to using HTTPS
url with Twisted Agent:
```
<class 'twisted.web._newclient.ResponseNeverReceived'>: [<twisted.python.failure.Failure OpenSSL.SSL.Error: [('SSL routines', 'tls_process_server_certificate', 'certificate verify failed')]>
```

The fix is to install certifi and provide the path to the trust store as
env var for OpenSSL to pick up.

Also includes a simplication of the core test_listen_port code.

1 files changed, 3 insertions, 11 deletions

diff --git a/deluge/core/core.py b/deluge/core/core.py
index 76abfc8ac..691a7c0d2 100644
--- a/deluge/core/core.py
+++ b/deluge/core/core.py
@@ -1121,23 +1121,15 @@ class Core(component.Component):
         port = self.get_listen_port()
         url = 'https://deluge-torrent.org/test_port.php?port=%s' % port
         agent = Agent(reactor, connectTimeout=30)
-        d = agent.request(
-            b'GET',
-            url.encode('utf-8'),
-        )
-
-        def on_get_page(response):
-            d = readBody(response)
-            d.addCallback(on_read_body)
-            return d
+        d = agent.request(b'GET', url.encode())
 
-        def on_read_body(body):
+        def on_get_page(body):
             return bool(int(body))
 
         def on_error(failure):
             log.warning('Error testing listen port: %s', failure)
 
-        d.addCallback(on_get_page)
+        d.addCallback(readBody).addCallback(on_get_page)
         d.addErrback(on_error)
 
         return d