Merge #96

96: Update pyopenssl to 17.3.0 r=mithrandi


There's a new version of [pyopenssl](https://pypi.python.org/pypi/pyopenssl) available.
You are currently using **17.2.0**. I have updated it to **17.3.0**



These links might come in handy:  <a href="https://pypi.python.org/pypi/pyopenssl">PyPI</a> | <a href="https://pyup.io/changelogs/pyopenssl/">Changelog</a> | <a href="https://pyopenssl.org/">Homepage</a> | <a href="http://pythonhosted.org/pyOpenSSL/">Docs</a> 



### Changelog
> 
>### 17.3.0

>-------------------


>Backward-incompatible changes:
>^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

>- Dropped support for Python 3.3.
>  `677 &lt;https://github.com/pyca/pyopenssl/pull/677&gt;`_
>- Removed the deprecated ``OpenSSL.rand`` module.
>  This is being done ahead of our normal deprecation schedule due to its lack of use and the fact that it was becoming a maintenance burden.
>  ``os.urandom()`` should be used instead.
>  `675 &lt;https://github.com/pyca/pyopenssl/pull/675&gt;`_


>Deprecations:
>^^^^^^^^^^^^^

>- Deprecated ``OpenSSL.tsafe``.
>  `673 &lt;https://github.com/pyca/pyopenssl/pull/673&gt;`_

>Changes:
>^^^^^^^^

>- Fixed a memory leak in ``OpenSSL.crypto.CRL``.
>  `690 &lt;https://github.com/pyca/pyopenssl/pull/690&gt;`_
>- Fixed a memory leak when verifying certificates with ``OpenSSL.crypto.X509StoreContext``.
>  `691 &lt;https://github.com/pyca/pyopenssl/pull/691&gt;`_


>----








*Got merge conflicts? Close this PR and delete the branch. I'll create a new PR for you.*

Happy merging! 🤖

requirements.txt

@@ -19,7 +19,7 @@ packaging==16.8
 pyasn1-modules==0.1.4
 pyasn1==0.3.3
 pycparser==2.18; platform_python_implementation != 'PyPy'
-pyopenssl==17.2.0
+pyopenssl==17.3.0
 pyparsing==2.2.0
 service-identity==17.0.0
 six==1.10.0