Exception when downloading ePub

[ekeller]

I am trying to download ePubs by overriding the build_index() method as described in the 'sticky: reusable code'. The files are located at

http://dp.x-cago.net/pdf/DePers.epub
http://pragprog.com/magazines/download/34.epub

The files are valid, I can drag them in Calibre OK -the first one is even created by Calibre. And everthing goes well, until in the end the process crashes with:

Creating EPUB Output...
67% Creating EPUB Output
# snip..
Failed to read image dimensions
Traceback (most recent call last):
  File "site-packages/calibre/ebooks/oeb/transforms/cover.py", line 124, in inspect_cover
  File "site-packages/calibre/utils/magick/draw.py", line 142, in identify_data
TypeError: must be string or read-only buffer, not lxml.etree._Element

Failed to read cover dimensions
EPUB output written to /home/edwin/Documents/git/calibre/pragpub/pragpub.epub
Output saved to   /home/edwin/Documents/git/calibre/pragpub/pragpub.epub

I tried replacing the downloaded 'cover_image.jpg' with Calibre's default cover, but that gave the same error.

Am I overlooking something or is there something broken?

Edwin

[ekeller]

I found a work around: convert the downloaded epub to OEB format and pass that on down the pipeline. See this thread

It even improves the formatting.