Use api to get driver schema file

Current code is assuming that the molecule driver are inside
a molecule_$driver python resource, which is not the case.
For instance, vagrant plugin is in molecule_plugins.

As a solution:
- extend driver class to provide a schema_file() member,
  allowing to return a path to the driver.json file,
- replace schema_v3 code to use molecule api and get the
  schema file path thanks to the new schema_file().

Signed-off-by: Arnaud Patard <apatard@hupstream.com>

src/molecule/driver/base.py

@@ -271,6 +271,9 @@ def get_playbook(self, step):
             return p
         return None
 
+    def schema_file(self):
+        return None
+
     def modules_dir(self):
         """Return path to ansible modules included with driver."""
         p = os.path.join(self._path, "modules")

src/molecule/driver/delegated.py

@@ -20,9 +20,11 @@
 """Delegated Driver Module."""
 
 import logging
+import os
 
 from molecule import util
 from molecule.api import Driver
+from molecule.data import __file__ as data_module
 
 LOG = logging.getLogger(__name__)
 
@@ -253,3 +255,6 @@ def _get_instance_config(self, instance_name):
     def sanity_checks(self):
         # Note(decentral1se): Cannot implement driver specifics are unknown
         pass
+
+    def schema_file(self):
+        return os.path.join(os.path.dirname(data_module), "driver.json")

src/molecule/model/schema_v3.py

@@ -19,14 +19,14 @@
 #  DEALINGS IN THE SOFTWARE.
 """Schema v3 Validation Module."""
 
-import importlib.resources as pkg_resources
 import json
 import logging
 import os
 
 from jsonschema import validate as jsonschema_validate
 from jsonschema.exceptions import ValidationError
 
+from molecule import api
 from molecule.data import __file__ as data_module
 
 LOG = logging.getLogger(__name__)
@@ -39,22 +39,18 @@ def validate(c):
 
     schema_files = [os.path.dirname(data_module) + "/molecule.json"]
     driver_name = c["driver"]["name"]
+
     driver_schema_file = None
+    if driver_name in api.drivers():
+        driver_schema_file = api.drivers()[driver_name].schema_file()
 
-    if driver_name == "delegated":
-        driver_schema_file = os.path.dirname(data_module) + "/driver.json"
+    if driver_schema_file is None:
+        msg = f"Driver {driver_name} does not provide a schema."
+        LOG.warning(msg)
+    elif not os.path.exists(driver_schema_file):
+        msg = f"Schema {driver_schema_file} for driver {driver_name} not found."
+        LOG.warning(msg)
     else:
-        try:
-            with pkg_resources.path(f"molecule_{driver_name}", "driver.json") as p:
-                driver_schema_file = p.as_posix()
-        except FileNotFoundError:
-            msg = f"No schema found in {driver_name} driver."
-            LOG.warning(msg)
-        except ModuleNotFoundError:
-            msg = f"{driver_name} driver is not installed."
-            LOG.warning(msg)
-
-    if driver_schema_file:
         schema_files.append(driver_schema_file)
 
     for schema_file in schema_files: