Python: How do I correctly decrypt the text sent from my Ruby script?

Question

I am trying to encrypt text locally in Ruby and decrypt it on the server with Python.

I post the encrypted phrase like so:

require "base64"
require "openssl"

public_key = OpenSSL::PKey::RSA.new File.read './publickey.pem'
encrypted = public_key.public_encrypt "Hello everyone. This is a secret phrase."

uri = URI('#...')
params = { "passage" => Base64.encode64(encrypted) }

response = HTTParty.post(
              uri,
              :body => params.to_json,
              :headers => {'Content-Type' => 'application/json'}
           )

My Python looks like this:

    f = open('./privatekey.pem', 'rb') # generated with ruby (OpenSSL::PKey::RSA.new 2048)
    private_key = RSA.importKey(f.read())
    f.close()

    return private_key.decrypt(encrypted)

This results in the error:

raise NotImplementedError("Use module Crypto.Cipher.PKCS1_OAEP instead")
NotImplementedError: Use module Crypto.Cipher.PKCS1_OAEP instead

So, I use PKCS1_OAEP:

    #...

    cipher_priv = PKCS1_OAEP.new(private_key)
    decrypted = cipher_priv.decrypt(encrypted)

This results in the error:

raise ValueError("Incorrect decryption.")
ValueError: Incorrect decryption.

…and I'm sent round in circles. If not PKCS1_OAEP what is the correct decryption?

How do I decrypt the text sent from Ruby to the Python server?