https://github.com/mozilla/bleach/pull/772

Index: setup.py
--- setup.py.orig
+++ setup.py
@@ -31,7 +31,7 @@ INSTALL_REQUIRES = [
 
 EXTRAS_REQUIRE = {
     "css": [
-        "tinycss2>=1.1.0,<1.5",
+        "tinycss2>=1.1.0,<2",
     ],
 }
 
