Skip SSL download test if SSL is not supported

This makes the testsuite pass entirely with a PyPI PyQt and OpenSSL 1.1

tests/end2end/features/downloads.feature

@@ -92,7 +92,8 @@ Feature: Downloading things from a website.
         Then no crash should happen
 
     Scenario: Downloading with SSL errors (issue 1413)
-        When I clear SSL errors
+        When SSL is supported
+        And I clear SSL errors
         And I set content.ssl_strict to ask
         And I set downloads.location.prompt to false
         And I download an SSL page

tests/end2end/features/test_downloads_bdd.py

@@ -23,6 +23,7 @@ import shlex
 
 import pytest
 import pytest_bdd as bdd
+from PyQt5.QtNetwork import QSslSocket
 bdd.scenarios('downloads.feature')
 
 
@@ -54,6 +55,12 @@ def clean_old_downloads(quteproc):
     quteproc.send_cmd(':download-clear')
 
 
+@bdd.when("SSL is supported")
+def check_ssl():
+    if not QSslSocket.supportsSsl():
+        pytest.skip("QtNetwork SSL not supported")
+
+
 @bdd.when("the unwritable dir is unwritable")
 def check_unwritable(tmpdir):
     unwritable = tmpdir / 'downloads' / 'unwritable'