Bump cryptography from 2.8.0 to 3.2

Bumps [cryptography](https://github.com/pyca/cryptography) from 2.8.0 to 3.2.
- [Release notes](https://github.com/pyca/cryptography/releases)
- [Changelog](https://github.com/pyca/cryptography/blob/master/CHANGELOG.rst)
- [Commits](pyca/cryptography@2.8...3.2)

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

requirements.txt

@@ -8,7 +8,7 @@ bdist-mpkg==0.5.0
 cffi==1.12.2
 click==7.0
 configparser==3.5.0
-cryptography==2.8.0
+cryptography==3.2
 enum34==1.1.6
 first==2.0.1
 Flask==1.1.1