Viewer works in 3.48, fails to open book in 4.x with ConversionFailure

[RKabel]

An epub book I created with ConTeXt displays fine in version 3 on W10/64. With version 4 (tested with 4.4, 4.5, 4.8) it fails with:\

Spoiler:

calibre, version 4.8.0
ERROR: Loading book failed: Failed to open the book at C:\Users\micro\Documents\Calibre Library\context mkiv\An Illustrated Taxonomy of Misquotat (90)\An Illustrated Taxonomy of Misq - context mkiv.epub. Click "Show details" for more info.

Traceback (most recent call last):
File "site-packages\calibre\gui2\viewer\ui.py", line 371, in _load_ebook_worker
File "site-packages\calibre\gui2\viewer\convert_book.py", line 234, in prepare_book
File "site-packages\calibre\gui2\viewer\convert_book.py", line 191, in do_convert
ConversionFailure: Failed to convert book: C:\Users\micro\Documents\Calibre Library\context mkiv\An Illustrated Taxonomy of Misquotat (90)\An Illustrated Taxonomy of Misq - context mkiv.epub with error:
InputFormatPlugin: EPUB Input running
on C:\Users\micro\Documents\Calibre Library\context mkiv\An Illustrated Taxonomy of Misquotat (90)\An Illustrated Taxonomy of Misq - context mkiv.epub
Failed to run pipe worker with command: from calibre.srv.render_book import viewer_main; viewer_main()
Python function terminated unexpectedly
Invalid input object: str (Error Code: 1)
Traceback (most recent call last):
File "site.py", line 114, in main
File "site.py", line 88, in run_entry_point
File "site-packages\calibre\utils\ipc\worker.py", line 189, in main
File "<string>", line 1, in <module>
File "site-packages\calibre\srv\render_book.py", line 848, in viewer_main
File "site-packages\calibre\srv\render_book.py", line 841, in render_for_viewer
File "site-packages\calibre\srv\render_book.py", line 820, in render
File "site-packages\calibre\srv\render_book.py", line 621, in process_exploded_book
File "site-packages\calibre\srv\render_book.py", line 305, in create_cover_page
File "site-packages\calibre\srv\render_book.py", line 258, in find_epub_cover
File "site-packages\calibre\ebooks\oeb\polish\cover.py", line 287, in find_cover_image_in_page
File "src/lxml/xpath.pxi", line 432, in lxml.etree.XPath.__call__
File "src/lxml/apihelpers.pxi", line 41, in lxml.etree._documentOrRaise
TypeError: Invalid input object: str

Debug log output:

calibre Debug log
calibre 4.8 [64bit] embedded-python: True is64bit: True
Windows-10-10.0.18362-SP0 Windows ('64bit', 'WindowsPE')
('Windows', '10', '10.0.18362')
Python 2.7.16+
Windows: ('10', '10.0.18362', 'SP0', u'Multiprocessor Free')
Interface language: None
calibre 4.8 [64bit] embedded-python: True is64bit: True
Windows-10-10.0.18362-SP0 Windows ('64bit', 'WindowsPE')
('Windows', '10', '10.0.18362')
Python 2.7.16+
Windows: ('10', '10.0.18362', 'SP0', u'Multiprocessor Free')
Interface language: None
Turning on automatic hidpi scaling
devicePixelRatio: 2.0
logicalDpi: 96.0 x 96.0
physicalDpi: 141.356521739 x 141.402061856
Using calibre Qt style: True
[0.00] Starting up...
[0.00] Showing splash screen...
[0.50] splash screen shown
[0.50] Initializing db...
[0.50] db initialized
[0.50] Constructing main UI...
[1.88] main UI initialized...
[1.88] Hiding splash screen
[12.17] splash screen hidden
[12.17] Started up in 12.17 seconds with 9 books
Worker Launch took: 0.0989999771118

Advice?

[kovidgoyal]

Run the check book tool in the calibre boo editor and fix the errors it reports.

[RKabel]

Thank you. That has shown a number of issues.

Is there a way to tell the checker to not complain about CSS3 constructs?

[theducks]

Originally Posted by RKabel

Thank you. That has shown a number of issues.

Is there a way to tell the checker to not complain about CSS3 constructs?

(I don't do EPUB3)
If you see CSS3 complaints, then there is a possibility they are valid because your document may not be a proper EPUB3 , but you are using constructs that don't belong to the current (EPUB2 ?)
OTOH you will always get some warnings if you work on AZW3 conversions (the REM vs em thingy)

[RKabel]

To be clear, I am complaining about error messages for css properties that are defined in EPUB3/CSS3 but not part of CSS2.1 -- such properties as hyphens, flex-flow, order, and many others. Also rem measures. Also @rules such as @counter-style.

The issue is that the messages saying that these violate CSS2.1 clutter the output of the checker function and make it difficult to see real errors. (There were some, and I am making progress fixing them.)

I understand that not all CSS3 features will be supported by some devices claiming EPUB3 support. Is there perhaps a conversion target device that allows full CSS3 specification?

[kovidgoyal]

Originally Posted by RKabel

Thank you. That has shown a number of issues.

Is there a way to tell the checker to not complain about CSS3 constructs?

No sadly the underlying library does not support checking against css3, until it does...