Calibre viewer freezes when opening news download converted to LRF

[Aimylios]

Description of the problem:
The Calibre viewer freezes when trying to open an LRF file that was previously converted by Calibre from an EPUB news download from within Calibre. I first get an error message saying "AttributeError:'TextStyle' object has no attribute 'fontweight'", and after confirming this with "OK" the viewer shows a progress bar and hangs. I then need to use the Task Manager to kill the process. Windows finally complains about a problem with "calibre-parallel.exe". Interestingly, I can open the file without any issues in the standalone viewer (i.e., when directly launched from Windows Explorer).

Steps to reproduce:
- launch Calibre
- download a news source of your choice (e.g., The Economist, but all news sources I tested were affected)
- convert the book to LRF ("Convert books", output format "LRF", keep all default settings)
- open the LRF ("View specific format", select LRF)

System information:
Calibre version 3.44
Windows 10 Pro (1809, 17763.557), 64 Bit
Locale: German (de_DE)

[Kovid Goyal (kovid)]

Fixed in branch master. The fix will be in the next release. calibre is usually released every alternate Friday.

 status fixreleased