Improve access of __annotations__ (#239)

## Changes
This is a continuation of #216, but with signed, verified commits.

## Tests
One test was added (in #216).  The last run in #216 passed all tests.

- [ ] `make test` run locally
- [ ] `make fmt` applied
- [ ] relevant integration tests applied

Author: MichaelSpece

databricks/sdk/core.py

@@ -702,10 +702,14 @@ def attributes(cls) -> Iterable[ConfigAttribute]:
         """ Returns a list of Databricks SDK configuration metadata """
         if hasattr(cls, '_attributes'):
             return cls._attributes
-        # Python 3.7 compatibility: getting type hints require extra hop, as described in
-        # "Accessing The Annotations Dict Of An Object In Python 3.9 And Older" section of
-        # https://docs.python.org/3/howto/annotations.html
-        anno = cls.__dict__['__annotations__']
+        if sys.version_info[1] >= 10:
+            import inspect
+            anno = inspect.get_annotations(cls)
+        else:
+            # Python 3.7 compatibility: getting type hints require extra hop, as described in
+            # "Accessing The Annotations Dict Of An Object In Python 3.9 And Older" section of
+            # https://docs.python.org/3/howto/annotations.html
+            anno = cls.__dict__['__annotations__']
         attrs = []
         for name, v in cls.__dict__.items():
             if type(v) != ConfigAttribute:

tests/test_core.py

@@ -207,3 +207,14 @@ def test_config_accounts_dod_is_accounts_host(config):
 def test_config_workspace_is_not_accounts_host(config):
     config.host = "https://westeurope.azuredatabricks.net"
     assert not config.is_account_client
+
+
+def test_config_can_be_subclassed():
+
+    class DatabricksConfig(Config):
+
+        def __init__(self):
+            super().__init__()
+
+    with pytest.raises(ValueError): # As opposed to `KeyError`.
+        DatabricksConfig()