Try to change little bit in your code as following
self.ec2conn = ec2.connect_to_region('eu-west-1',
aws_access_key_id=self.access_key,
aws_secret_access_key=self.secret_key)
print(self.get_instances())
Or
region = ec2.get_region('eu-west-1')
self.ec2conn = ec2.connection.EC2Connection(self.access_key,
self.secret_key, region=region)
print(self.get_instances())
Remember that ec2.connect_to_region
and ec2.connection.EC2Connection
both returns ec2.connection.EC2Connection
object. Refer here