From: Ole Streicher <olebole@debian.org>
Date: Fri, 10 Aug 2018 08:35:39 +0200
Subject: Emulate importlib.resources for Python <= 3.6

---
 asdf/tests/helpers.py | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/asdf/tests/helpers.py b/asdf/tests/helpers.py
index 24ccb10..8c999b1 100644
--- a/asdf/tests/helpers.py
+++ b/asdf/tests/helpers.py
@@ -50,16 +50,17 @@ __all__ = ['get_test_data_path', 'assert_tree_match', 'assert_roundtrip_tree',
 
 
 def get_test_data_path(name, module=None):
-    if resources is None:
-        raise RuntimeError("The importlib_resources package is required to get"
-                           " test data on systems with Python < 3.7")
-
     if module is None:
         from . import data as test_data
         module = test_data
 
-    with resources.path(module, name) as path:
-        return str(path)
+    if resources is not None:
+        with resources.path(module, name) as path:
+            return str(path)
+    elif name:
+        return os.path.join(os.path.dirname(module.__file__), name)
+    else:
+        return os.path.dirname(module.__file__)
 
 
 def assert_tree_match(old_tree, new_tree, ctx=None,
