Added constructors

[roeman]

This seems to fix the issue with Python scripts not being available for use in conditional build steps.

[roeman]

I see someone else submitted a change for fixing this issue, but mine didn't seem to work without this extra code?

[elitenas]

@olivergondza any way to merge this in? This change is much needed and highly requested

[olivergondza]

@mazimkhan, as a maintainer, please take a look.

[elitenas]

Hi @mazimkhan,

Please take a look at these conversations...

https://issues.jenkins.io/browse/JENKINS-12483
https://issues.jenkins.io/browse/JENKINS-40800

According to this web page (https://wiki.jenkins-ci.org/display/JENKINS/Conditional+BuildStep+Plugin), the problem is because the Python Plugin "does not provide a @DataBoundConstructor constructor and/or the Descriptor does not extend hudson.tasks.BuildStepDescriptor."

[elitenas]

@olivergondza, is there any one else who has the ability to merge this PR?

[mazimkhan]

Apologies for this late reply. I don't see the option to merge this PR. Not sure it this is due to failing CI.

Besides, I no longer use Jenkins or maintain this plugin. If someone else wants to take over, please do.