tox: add an 'extras' to the python package

The python package extras is a way to express optional dependencies.
Since sambacc can work without jsonschema for validation, we create
an extra called "validation" that requires jsonschema.

Signed-off-by: John Mulligan <[email protected]>

Author: phlogistonjohn

setup.cfg

@@ -27,3 +27,7 @@ share/sambacc/examples =
   examples/example1.json
   examples/minimal.json
   examples/addc.json
+
+[options.extras_require]
+validation =
+    jsonschema>=4.10

tox.ini

@@ -12,6 +12,7 @@ deps =
     pytest
     pytest-cov
     dnspython
+    -e .[validation]
 commands =
     py.test -v tests --cov=sambacc --cov-report=html {posargs}