fix: Fix LRO method test and rest test coverage (#1433)

This does:
1) fixes LRO method mock value which for watever reason worked under proto 3.x.x (cpp implementaiton) but does not work under proto 4
2) Add `NO COVER` to mock imports in tests as those lines are mutually exclusive depending on the python version it is runniin gunder.

Co-authored-by: Anthonios Partheniou <partheniou@google.com>

gapic/templates/tests/unit/gapic/%name_%version/%sub/test_%service.py.j2

@@ -7,8 +7,8 @@ import os
 # try/except added for compatibility with python < 3.8
 try:
     from unittest import mock
-    from unittest.mock import AsyncMock
-except ImportError:
+    from unittest.mock import AsyncMock  # pragma: NO COVER
+except ImportError:  # pragma: NO COVER
     import mock
 
 import grpc

gapic/templates/tests/unit/gapic/%name_%version/%sub/test_macros.j2

@@ -1172,7 +1172,7 @@ def test_{{ method_name }}_rest_interceptors(null_interceptor):
         ]
         pre.return_value = request, metadata
         {% if not method.void %}
-        post.return_value = {{ method.output.ident }}
+        post.return_value = {{ method.output.ident }}()
         {% endif %}
 
         client.{{ method_name }}(request, metadata=[("key", "val"), ("cephalopod", "squid"),])

tests/integration/goldens/asset/tests/unit/gapic/asset_v1/test_asset_service.py

@@ -17,8 +17,8 @@
 # try/except added for compatibility with python < 3.8
 try:
     from unittest import mock
-    from unittest.mock import AsyncMock
-except ImportError:
+    from unittest.mock import AsyncMock  # pragma: NO COVER
+except ImportError:  # pragma: NO COVER
     import mock
 
 import grpc

tests/integration/goldens/credentials/tests/unit/gapic/credentials_v1/test_iam_credentials.py

@@ -17,8 +17,8 @@
 # try/except added for compatibility with python < 3.8
 try:
     from unittest import mock
-    from unittest.mock import AsyncMock
-except ImportError:
+    from unittest.mock import AsyncMock  # pragma: NO COVER
+except ImportError:  # pragma: NO COVER
     import mock
 
 import grpc

tests/integration/goldens/eventarc/tests/unit/gapic/eventarc_v1/test_eventarc.py

@@ -17,8 +17,8 @@
 # try/except added for compatibility with python < 3.8
 try:
     from unittest import mock
-    from unittest.mock import AsyncMock
-except ImportError:
+    from unittest.mock import AsyncMock  # pragma: NO COVER
+except ImportError:  # pragma: NO COVER
     import mock
 
 import grpc

tests/integration/goldens/logging/tests/unit/gapic/logging_v2/test_config_service_v2.py

@@ -17,8 +17,8 @@
 # try/except added for compatibility with python < 3.8
 try:
     from unittest import mock
-    from unittest.mock import AsyncMock
-except ImportError:
+    from unittest.mock import AsyncMock  # pragma: NO COVER
+except ImportError:  # pragma: NO COVER
     import mock
 
 import grpc

tests/integration/goldens/logging/tests/unit/gapic/logging_v2/test_logging_service_v2.py

@@ -17,8 +17,8 @@
 # try/except added for compatibility with python < 3.8
 try:
     from unittest import mock
-    from unittest.mock import AsyncMock
-except ImportError:
+    from unittest.mock import AsyncMock  # pragma: NO COVER
+except ImportError:  # pragma: NO COVER
     import mock
 
 import grpc

tests/integration/goldens/logging/tests/unit/gapic/logging_v2/test_metrics_service_v2.py

@@ -17,8 +17,8 @@
 # try/except added for compatibility with python < 3.8
 try:
     from unittest import mock
-    from unittest.mock import AsyncMock
-except ImportError:
+    from unittest.mock import AsyncMock  # pragma: NO COVER
+except ImportError:  # pragma: NO COVER
     import mock
 
 import grpc

tests/integration/goldens/redis/tests/unit/gapic/redis_v1/test_cloud_redis.py

@@ -17,8 +17,8 @@
 # try/except added for compatibility with python < 3.8
 try:
     from unittest import mock
-    from unittest.mock import AsyncMock
-except ImportError:
+    from unittest.mock import AsyncMock  # pragma: NO COVER
+except ImportError:  # pragma: NO COVER
     import mock
 
 import grpc