Block PyOpenSSL to prevent SELinux execmem in wsgi
    
    Some dependencies like Dogtag's pki.client library and custodia use
    python-requsts to make HTTPS connection. python-requests prefers
    PyOpenSSL over Python's stdlib ssl module. PyOpenSSL is build on top
    of python-cryptography which trigger a execmem SELinux violation
    in the context of Apache HTTPD (httpd_execmem).
    
    When requests is imported, it always tries to import pyopenssl glue
    code from urllib3's contrib directory. The import of PyOpenSSL is
    enough to trigger the SELinux denial.
    
    Block any import of PyOpenSSL's SSL module in wsgi by raising an
    ImportError. The block is compatible with new python-requests with
    unbundled urllib3, too.
    
    Fixes: https://pagure.io/freeipa/issue/5442
    Fixes: RHBZ#1491508
    Signed-off-by: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>
    Reviewed-By: Tomas Krizek <tkrizek@redhat.com>