[stumped]

epub to azw3 is adding line height declarations to CSS - is this a bug & can this be disabled ?
I do not recall seeing this in the past, so maybe it did not happen in older versions of calibre. My sideloaded azw books look awful after such conversion - lines are far too close together, and the device options do not expand them.
( I tried disable font scaling in conversion preferences - that had no effect )

I removed all line heights from each class of the epub css before converting it e.g.
.calibre {
adobe-hyphenate: none;
display: block;
font-size: 1.1em;

margin-bottom: 0;
margin-left: 5pt;
margin-right: 5pt;
margin-top: 0;
orphans: 1;
padding-left: 0;
padding-right: 0;
text-align: justify;
widows: 1
}
but in every class in the AZW css, there is now an added line-height delcaration ( I have marked it in bold below) e.g.

.calibre {
adobe-hyphenate: none;
display: block;
font-size: 1.1em;
line-height: 1.2;
margin-bottom: 0;
margin-left: 5pt;
margin-right: 5pt;
margin-top: 0;
orphans: 1;

PS a conversion from epub to mobi looks equally bad.

it is not an issue with the specific book, I converted another chosen at random eub with same outcome.

PPS I stumbled across another bug ? or install error? I went to preferences to inspect all the conversion options, but when I click on output options I get
ImportError: No module named output_config
- here is the detail:
calibre 2.56 [64bit] embedded-python: True is64bit: True
Windows-8-6.2.9200 Windows ('64bit', 'WindowsPE')
('Windows', '8', '6.2.9200')
Python 2.7.9
Windows: ('8', '6.2.9200', '', 'Multiprocessor Free')
Successfully initialized third party plugins: DeDRM && K4PC, K4Mac, Kindle Mobi and Topaz DeDRM && Inept PDF DeDRM && Inept Epub DeDRM && Count Pages && Copy Cover To Device && Quality Check && Modify ePub && Open With && Overdrive Link && Resize Cover && View Manager && Open EPUB In Editor && Overdrive Link
Traceback (most recent call last):
File "site-packages\calibre\gui2\preferences\main.py", line 292, in show_plugin
File "site-packages\calibre\customize\__init__.py", line 663, in create_widget
File "importlib\__init__.py", line 37, in import_module
ImportError: No module named output_config