python: sanitize blank line usage

python: sanitize blank line usage

Coding style expects 1 blank line between each method and 2 blank lines
before each class.

docs/apibuild.py:171:5: E303 too many blank lines (2)
    def set_header(self, header):
    ^
docs/apibuild.py:230:1: E302 expected 2 blank lines, found 1
class index:
^
docs/apibuild.py:175:5: E301 expected 1 blank line, found 0
    def set_module(self, module):
    ^
...more...

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>