Update ixia_fixture to fix collection errors (#2570)

* Update ixia_fixture to fix collection errors

Errors were reported during pytest collecting test cases because
ImportError for IxNetworkApi, which is available only on ixia devices.
This commit attempts to catch import exception and skips cases when
exception is caught.

Signed-off-by: bingwang <[email protected]>

* Fix typo.

Signed-off-by: bingwang <[email protected]>

Author: bingwang-ms

tests/common/ixia/ixia_fixtures.py

@@ -6,7 +6,10 @@
 
 import pytest
 from ixnetwork_restpy import SessionAssistant
-from ixnetwork_open_traffic_generator.ixnetworkapi import IxNetworkApi
+try:
+    from ixnetwork_open_traffic_generator.ixnetworkapi import IxNetworkApi
+except ImportError as e:
+    raise pytest.skip.Exception("Test case is skipped: " + repr(e), allow_module_level=True)
 
 @pytest.fixture(scope = "module")
 def ixia_api_serv_ip(tbinfo):
@@ -149,14 +152,14 @@ def ixia_api_server_session(
 
 @pytest.fixture(scope = "function")
 def ixia_api(ixia_api_serv_ip,
-             ixia_api_serv_port, 
-             ixia_api_serv_user, 
+             ixia_api_serv_port,
+             ixia_api_serv_user,
              ixia_api_serv_passwd):
 
     api_session = IxNetworkApi(address=ixia_api_serv_ip,
                                port=ixia_api_serv_port,
                                username=ixia_api_serv_user,
                                password=ixia_api_serv_passwd)
-    
+
     yield api_session
     api_session.assistant.Session.remove()