compatibility with breaking changes to the ast module

new in 3.10, also backported to 3.8 and 3.9: https://github.com/python/cpython/pull/20649
In fact, our generation of some Literals has been invalid since Python
3.4, fix that too.

beets/util/functemplate.py

@@ -73,15 +73,26 @@ def ex_literal(val):
     """An int, float, long, bool, string, or None literal with the given
     value.
     """
-    if val is None:
-        return ast.Name('None', ast.Load())
-    elif isinstance(val, six.integer_types):
-        return ast.Num(val)
-    elif isinstance(val, bool):
-        return ast.Name(bytes(val), ast.Load())
-    elif isinstance(val, six.string_types):
-        return ast.Str(val)
-    raise TypeError(u'no literal for {0}'.format(type(val)))
+    if sys.version_info[:2] < (3, 4):
+        if val is None:
+            return ast.Name('None', ast.Load())
+        elif isinstance(val, six.integer_types):
+            return ast.Num(val)
+        elif isinstance(val, bool):
+            return ast.Name(bytes(val), ast.Load())
+        elif isinstance(val, six.string_types):
+            return ast.Str(val)
+        raise TypeError(u'no literal for {0}'.format(type(val)))
+    elif sys.version_info[:2] < (3, 6):
+        if val in [None, True, False]:
+            return ast.NameConstant(val)
+        elif isinstance(val, six.integer_types):
+            return ast.Num(val)
+        elif isinstance(val, six.string_types):
+            return ast.Str(val)
+        raise TypeError(u'no literal for {0}'.format(type(val)))
+    else:
+        return ast.Constant(val)
 
 
 def ex_varassign(name, expr):

docs/changelog.rst

@@ -213,6 +213,7 @@ Fixes:
 * :doc:`/plugins/lyrics`: Fix crash when writing ReST files for a query without
   results or fetched lyrics
   :bug:`2805`
+* Adapt to breaking changes in Python's ``ast`` module in 3.8
 
 For plugin developers: