bpo-41887: omit leading spaces/tabs on ast.literal_eval (#22469)

Also document that eval() does this (the same way).
diff --git a/Lib/test/test_ast.py b/Lib/test/test_ast.py
index 5f57ce8..be4b0f7 100644
--- a/Lib/test/test_ast.py
+++ b/Lib/test/test_ast.py
@@ -1005,6 +1005,12 @@
         malformed = ast.Dict(keys=[ast.Constant(1)], values=[ast.Constant(2), ast.Constant(3)])
         self.assertRaises(ValueError, ast.literal_eval, malformed)
 
+    def test_literal_eval_trailing_ws(self):
+        self.assertEqual(ast.literal_eval("    -1"), -1)
+        self.assertEqual(ast.literal_eval("\t\t-1"), -1)
+        self.assertEqual(ast.literal_eval(" \t -1"), -1)
+        self.assertRaises(IndentationError, ast.literal_eval, "\n -1")
+
     def test_bad_integer(self):
         # issue13436: Bad error message with invalid numeric values
         body = [ast.ImportFrom(module='time',