How to add jinja2 extension to the custom CKAN theme?

Question

Is there any way to add Hamlish-jinja extension to my custom CKAN theme without editing CKAN files?

I was able to make it work by editing CKAN ckan/config/environment.py (after line 334) file.

# Create Jinja2 environment
env = jinja_extensions.Environment(
    loader=jinja_extensions.CkanFileSystemLoader(template_paths),
    autoescape=True,
    extensions=['jinja2.ext.do', 'jinja2.ext.with_',
                jinja_extensions.SnippetExtension,
                jinja_extensions.CkanExtend,
                jinja_extensions.CkanInternationalizationExtension,
                jinja_extensions.LinkForExtension,
                jinja_extensions.ResourceExtension,
                jinja_extensions.UrlForStaticExtension,
                jinja_extensions.UrlForExtension,
                HamlishExtension]
)