bonfire: fix build

The requirement's constraint for `pythonPackages.keyring` didn't allow
keyring v11. However it has been bumped in 93a16a2ace
by @FRidh.

Current failure: https://nix-cache.s3.amazonaws.com/log/2nw5adfx86jwiax32mn11kqpc35xwhsh-bonfire-unstable-2017-01-19.drv
See ticket #36453

pkgs/tools/misc/bonfire/default.nix

@@ -20,7 +20,7 @@ buildPythonApplication rec {
     # https://github.com/blue-yonder/bonfire/pull/24
     substituteInPlace requirements.txt \
       --replace "arrow>=0.5.4,<0.8" "arrow>=0.5.4,<0.13" \
-      --replace "keyring>=9,<10"    "keyring>=9,<11"
+      --replace "keyring>=9,<10"    "keyring>=9,<=11"
     # pip fails when encountering the git hash for the package version
     substituteInPlace setup.py \
       --replace "version=version," "version='${version}',"