Bump cryptography from 2.3.1 to 3.2

Bumps [cryptography](https://github.com/pyca/cryptography) from 2.3.1 to 3.2.
- [Release notes](https://github.com/pyca/cryptography/releases)
- [Changelog](https://github.com/pyca/cryptography/blob/master/CHANGELOG.rst)
- [Commits](pyca/cryptography@2.3.1...3.2)

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

setup.py

@@ -13,7 +13,7 @@
     "Sphinx==1.8.1",
     "pyOpenSSL==18.0.0",
     "cffi==1.11.5",
-    "cryptography==2.3.1",
+    "cryptography==3.2",
     "expiringdict==1.1.4",
     "psutil==5.6.6",
     "lazy==1.3",