Fix dependency issue

- Set pyopenssl >=19.1 so that it is compatable with cryptography
  >=3.3.0
- Revert cryptography requriement to 3.3

requirements.txt

@@ -2,8 +2,8 @@
 
 argo-ams-library
 certifi<2020.4.5.2  # Used by AMS (via requests), 2020.4.5.2 dropped support for Python 2
-pyopenssl<=21.0.0  # 22.0.0 dropped support for Python 2
-cryptography==3.2.0  # Crypto dropped support for Python 2 after 3.3
+pyopenssl >=19.1.0, <=21.0.0  # 22.0.0 dropped support for Python 2
+cryptography==3.3.0  # Crypto dropped support for Python 2 after 3.3
 stomp.py<5.0.0
 python-daemon<=2.3.0  # 2.3.1 dropped support for Python 2
 python-ldap<3.4.0  # python-ldap-3.4.0 dropped support for Python 2

setup.py

@@ -51,11 +51,11 @@ def main():
           download_url='https://github.com/apel/ssm/releases',
           license='Apache License, Version 2.0',
           install_requires=[
-              'cryptography==3.2.0',
+              'cryptography==3.3.0',
               'stomp.py<5.0.0',
               'python-ldap<3.4.0',
               'setuptools',
-              'pyopenssl<=21.0.0',
+              'pyopenssl >=19.1.0, <=21.0.0',
           ],
           extras_require={
               'AMS': ['argo-ams-library', 'certifi<2020.4.5.2', ],