Revert "Use native OpenSSL module to generate `passkey.pem`"

This reverts commit 0dac5ea508.

Relying on pyOpenSSL is the Ansible way of doing things, but is
impractical and annoying for users.

`openssl` is easily available on most servers, even by default.
We'd better use that.

docs/configuring-playbook-bridge-appservice-irc.md

@@ -4,8 +4,6 @@ The playbook can install and configure [matrix-appservice-irc](https://github.co
 
 See the project's [documentation](https://github.com/TeDomum/matrix-appservice-irc/blob/master/HOWTO.md) to learn what it does and why it might be useful to you.
 
-The Appservice IRC bridge configuration using Ansible will require that you have `python-pyOpenSSL` installed on your local machine.
-
 You'll need to use the following playbook configuration:
 
 ```yaml

roles/matrix-synapse/tasks/ext/appservice-irc/setup.yml

@@ -22,12 +22,13 @@
     group: "{{ matrix_user_username }}"
   when: "matrix_appservice_irc_enabled"
 
-- name: Generate matrix-appservice-irc passkey if it doesn't exist
-  openssl_privatekey:
+- stat:
     path: "{{ matrix_appservice_irc_base_path }}/passkey.pem"
-    size: 2048
-    force: false
-  when: "matrix_appservice_irc_enabled"
+  register: irc_passkey_file
+
+- name: Generate matrix-appservice-irc passkey if it doesn't exist
+  shell: /usr/bin/openssl genpkey -out {{ matrix_appservice_irc_base_path }}/passkey.pem -outform PEM -algorithm RSA -pkeyopt rsa_keygen_bits:2048
+  when: "matrix_appservice_irc_enabled and irc_passkey_file.stat.exists == False"
 
 - name: Ensure matrix-appservice-irc.service installed
   template: