tests: switch simple http server to python3

Python2 is phased out and not available anymore in some templates.

qubes/tests/integ/dom0_update.py

@@ -194,7 +194,7 @@ Test package
         if self.repo_running:
             return
         self.repo_proc = self.loop.run_until_complete(self.updatevm.run(
-            'cd /tmp/repo && python -m SimpleHTTPServer 8080',
+            'cd /tmp/repo && python3 -m http.server 8080',
             stdout=subprocess.DEVNULL,
             stderr=subprocess.STDOUT))
         self.repo_running = True

qubes/tests/integ/network.py

@@ -1443,12 +1443,12 @@ SHA256:
         if self.template.count("debian") or self.template.count("whonix"):
             self.create_repo_apt()
             self.loop.run_until_complete(self.netvm_repo.run(
-                'cd /tmp/apt-repo && python -m SimpleHTTPServer 8080',
+                'cd /tmp/apt-repo && python3 -m http.server 8080',
                 stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL))
         elif self.template.count("fedora"):
             self.create_repo_yum()
             self.loop.run_until_complete(self.netvm_repo.run(
-                'cd /tmp/yum-repo && python -m SimpleHTTPServer 8080',
+                'cd /tmp/yum-repo && python3 -m http.server 8080',
                 stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL))
         else:
             # not reachable...