Do not crash if no console port is available for VBox

I don't know how user manage to fall in this situation.

Fix #127

tests/modules/virtualbox/test_virtualbox_manager.py

@@ -38,12 +38,14 @@ def test_vm_invalid_vboxmanage_path(manager):
         with pytest.raises(VirtualBoxError):
             manager.find_vboxmanage()
 
+
 def test_vm_non_executable_vboxmanage_path(manager):
     tmpfile = tempfile.NamedTemporaryFile()
     with patch("gns3server.config.Config.get_section_config", return_value={"vboxmanage_path": tmpfile.name}):
         with pytest.raises(VirtualBoxError):
             manager.find_vboxmanage()
 
+
 def test_vm_invalid_executable_name_vboxmanage_path(manager, tmpdir):
     path = str(tmpdir / "vpcs")
     with open(path, "w+") as f:
@@ -54,6 +56,7 @@ def test_vm_invalid_executable_name_vboxmanage_path(manager, tmpdir):
         with pytest.raises(VirtualBoxError):
             manager.find_vboxmanage()
 
+
 def test_vboxmanage_path(manager, tmpdir):
     path = str(tmpdir / "VBoxManage")
     with open(path, "w+") as f:
@@ -62,4 +65,3 @@ def test_vboxmanage_path(manager, tmpdir):
     tmpfile = tempfile.NamedTemporaryFile()
     with patch("gns3server.config.Config.get_section_config", return_value={"vboxmanage_path": path}):
         assert manager.find_vboxmanage() == path
-

tests/modules/virtualbox/test_virtualbox_vm.py

@@ -54,4 +54,3 @@ def test_vm_invalid_virtualbox_api_version(loop, project, manager):
         with pytest.raises(VirtualBoxError):
             vm = VirtualBoxVM("test", "00010203-0405-0607-0809-0a0b0c0d0e0f", project, manager, "test", False)
             loop.run_until_complete(asyncio.async(vm.create()))
-