Try to fix the Nix build

nix/setup.cfg.patch

+diff --git a/setup.cfg b/setup.cfg
+index 3856a101..371a19b3 100644
+--- a/setup.cfg
++++ b/setup.cfg
+@@ -38,7 +38,7 @@ install_requires =
+     python-challenge-bypass-ristretto
+     # Inherit our Twisted dependency from tahoe-lafs so we don't accidentally
+     # get the extras wrong here and break stuff.
+-    tahoe-lafs==1.14.0
++    tahoe-lafs
+     treq
+ 
+ [versioneer]

zkapauthorizer.nix

@@ -27,6 +27,12 @@ buildPythonPackage rec {
     sphinx
   ];
 
+  patches = [
+    # Remove the Tahoe-LAFS version pin in distutils config.  We have our own
+    # pinning and also our Tahoe-LAFS package has a bogus version number. :/
+    ./nix/setup.cfg.patch
+  ];
+
   propagatedBuildInputs = [
     attrs
     zope_interface