969939 /usr/bin/calibre-parallel:ValueError:/usr/bin/calibre-parallel@19:main:gui_convert_override:gui_convert:run:convert:convert:to_opf2:_to_ncx:to_ncx:element:lxml.etree.SubElement (src/lxml/lxml.etree.c:53668):lxml.etree._makeSubElement (src/lxml/lxml.etree.c:12435):lxml.etree._makeSubElement (src/lxml/lxml.etree.c:12360):lxml.etree._initNodeAttributes (src/lxml/lxml.etree.c:13270):lxml.etree._utf8 (src/lxml/lxml.etree.c:22060) 967208 /usr/bin/calibre-parallel:ValueError:/usr/bin/calibre-parallel@19:main:set_metadata_ 1873079 /usr/bin/calibre-parallel:ValueError:/usr/bin/calibre-parallel@20:main:@1:viewer_main:render_for_viewer:render:extract_book:__init__ 2003713 /usr/bin/calibre-parallel:ValueError:/usr/bin/calibre-parallel@21:main:@1:viewer_main:render_for_viewer:render:extract_book:__init__ 667133 /usr/bin/calibre-parallel:ValueError::main:gui_convert:run:__call__:convert:__init__ 861032 /usr/bin/calibre-parallel:ValueError::main:gui_convert_override:gui_convert:run 810151 /usr/bin/calibre-parallel:ValueError::main:gui_convert_override:gui_convert:run:__call__:convert:extract_content:fromstring:_parse:_convert_tree:_convert_children:_convert_children:_convert_children:_convert_children:_convert_children:_convert_children:_convert_children:_convert_children:_convert_children:_convert_children:_convert_children:_convert_children:_convert_children:_convert_children:_convert_children:_convert_children:_convert_children:_convert_children:_convert_children:_append_text:(src/lxml/lxml.etree.c:36134):(src/lxml/lxml.etree.c:17141):(src/lxml/lxml.etree.c:22211)