Let type annotation syntax to work with Python 3.9

And fix the development Python to 3.9, so that
local testing catches problems like this sooner.

Author: ctrueden

dev-environment.yml

@@ -18,7 +18,7 @@ name: scyjava-dev
 channels:
   - conda-forge
 dependencies:
-  - python >= 3.9
+  - python = 3.9
   # Project dependencies
   - jpype1 >= 1.3.0
   - jgo

src/scyjava/config.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import enum as _enum
 import logging as _logging
 import os as _os

src/scyjava/inspect.py

@@ -2,6 +2,8 @@
 High-level convenience functions for inspecting Java objects.
 """
 
+from __future__ import annotations
+
 from sys import stdout as _stdout
 
 from scyjava import _introspect