sonic-yang-models: Specify test dependencies under extra_requires

Newer versions of pip/setuptools don't support test_requires, and the
current standard is to specify any extra dependencies (such as those
required for testing) under extra_requires.

Therefore, specify the testing dependencies under extra_requires. These
can be installed via pip using `pip install '.[testing]'`.

Signed-off-by: Saikrishna Arcot <sarcot@microsoft.com>

src/sonic-yang-models/setup.py

@@ -69,6 +69,12 @@ setup(
         'pytest-runner',
         'wheel'
     ],
+    extras_require = {
+        "testing": [
+            'pytest',
+            'ijson==3.2.3'
+        ],
+    },
     include_package_data=True,
     keywords='sonic-yang-models',
     name='sonic-yang-models',