Avoid resource warning from dev scripts installed editable

Avoid ` ResourceWarning: unclosed file <_io.TextIOWrapper name='whatever' mode='r' encoding='UTF-8'>` on dev scripts installed editable

setuptools/script (dev).tmpl

@@ -2,4 +2,5 @@
 __requires__ = %(spec)r
 __import__('pkg_resources').require(%(spec)r)
 __file__ = %(dev_path)r
-exec(compile(open(__file__).read(), __file__, 'exec'))
+with open(__file__) as f:
+    exec(compile(f.read(), __file__, 'exec'))