Add six to `install_requires`

1 files changed, 1 insertions, 1 deletions

diff --git a/setup.py b/setup.py
index 56997532..c62a1bb4 100644
--- a/setup.py
+++ b/setup.py
@@ -90,6 +90,6 @@ setup(
     # TODO 3.0: alternately, given how prevalent ed25519 is now, and how we use
     # invoke for (increasing) subproc stuff, consider making the default flavor
     # "full" and adding a "minimal" or similar that is just-crypto?
-    install_requires=["bcrypt>=3.1.3", "cryptography>=2.5", "pynacl>=1.0.1"],
+    install_requires=["bcrypt>=3.1.3", "cryptography>=2.5", "pynacl>=1.0.1", "six"],
     extras_require=extras_require,
 )