Fix AST nodes for Python 3 and enable dependent test_uri (#18597)

* Enable tests on python 3 for uri

* Added one more node type to SAFE_NODES into safe_eval module.

ast.USub represents unary operators. This is necessary for
parsing some unusual but still valid JSON files during testing
with Python 3.

lib/ansible/template/safe_eval.py

@@ -69,6 +69,7 @@ def safe_eval(expr, locals={}, include_exceptions=False):
             ast.Name,
             ast.Str,
             ast.Sub,
+            ast.USub,
             ast.Tuple,
             ast.UnaryOp,
         )