[Leonatus]

Windows 10, 32 bit. Calibre Version 2.77. Each time I try to convert epub to kepub, I receive this error message:

calibre, version 2.77.0 (win32, embedded-python: True)
Konvertierungsfehler: Fehlgeschlagen: Buch 1 von 1 (Im grünen Tann) konvertieren

Buch 1 von 1 (Im grünen Tann) konvertieren
C:\Program Files\Calibre2\pylib.zip\dateutil\parser.py:339: UnicodeWarning: Unicode equal comparison failed to convert both arguments to Unicode - interpreting them as being unequal
Resolved conversion options
calibre version: 2.77.0
{'asciiize': False,
 'author_sort': None,
 'authors': None,
 'base_font_size': 0.0,
 'book_producer': None,
 'change_justification': u'original',
 'chapter': u"//*[((name()='h1' or name()='h2') and re:test(., '\\s*((chapter|book|section|part)\\s+)|((prolog|prologue|epilogue)(\\s+|$))', 'i')) or @class = 'chapter']",
 'chapter_mark': u'pagebreak',
 'comments': None,
 'cover': u'C:\\Users\\JRGEN~1\\AppData\\Local\\Temp\\calibre_e8t66c\\4futth.jpeg',
 'debug_pipeline': None,
 'dehyphenate': True,
 'delete_blank_paragraphs': True,
 'disable_font_rescaling': False,
 'dont_split_on_page_breaks': False,
 'duplicate_links_in_toc': False,
 'embed_all_fonts': False,
 'embed_font_family': None,
 'enable_heuristics': False,
 'epub_flatten': False,
 'epub_inline_toc': False,
 'epub_toc_at_end': False,
 'expand_css': False,
 'extra_css': u'@page {margin: 5pt}',
 'extract_to': None,
 'filter_css': u'',
 'fix_indents': True,
 'flow_size': 260,
 'font_size_mapping': None,
 'format_scene_breaks': True,
 'html_unwrap_factor': 0.4,
 'input_encoding': None,
 'input_profile': <calibre.customize.profiles.InputProfile object at 0x052FE7B0>,
 'insert_blank_line': False,
 'insert_blank_line_size': 0.5,
 'insert_metadata': False,
 'isbn': None,
 'italicize_common_cases': True,
 'keep_ligatures': False,
 'kepub_clean_markup': True,
 'kepub_disable_hyphenation': False,
 'kepub_hyphenate': True,
 'kepub_replace_lang': True,
 'language': None,
 'level1_toc': None,
 'level2_toc': None,
 'level3_toc': None,
 'line_height': 0.0,
 'linearize_tables': False,
 'margin_bottom': 5.0,
 'margin_left': 5.0,
 'margin_right': 5.0,
 'margin_top': 5.0,
 'markup_chapter_headings': True,
 'max_toc_links': 50,
 'minimum_line_height': 120.0,
 'no_chapters_in_toc': False,
 'no_default_epub_cover': False,
 'no_inline_navbars': False,
 'no_svg_cover': False,
 'output_profile': <calibre.customize.profiles.KoboReaderOutput object at 0x052FEBD0>,
 'page_breaks_before': u'/',
 'prefer_metadata_cover': False,
 'preserve_cover_aspect_ratio': False,
 'pretty_print': True,
 'pubdate': None,
 'publisher': None,
 'rating': None,
 'read_metadata_from_opf': u'C:\\Users\\JRGEN~1\\AppData\\Local\\Temp\\calibre_e8t66c\\vjhvrc.opf',
 'remove_fake_margins': True,
 'remove_first_image': False,
 'remove_paragraph_spacing': False,
 'remove_paragraph_spacing_indent_size': 1.5,
 'renumber_headings': True,
 'replace_scene_breaks': u'',
 'search_replace': '[]',
 'series': None,
 'series_index': None,
 'smarten_punctuation': False,
 'sr1_replace': None,
 'sr1_search': None,
 'sr2_replace': None,
 'sr2_search': None,
 'sr3_replace': None,
 'sr3_search': None,
 'start_reading_at': None,
 'subset_embedded_fonts': False,
 'tags': None,
 'timestamp': None,
 'title': None,
 'title_sort': None,
 'toc_filter': None,
 'toc_threshold': 6,
 'toc_title': None,
 'transform_css_rules': '[]',
 'unsmarten_punctuation': False,
 'unwrap_lines': True,
 'use_auto_toc': False,
 'verbose': 2}
InputFormatPlugin: EPUB Input running
on C:\Users\JRGEN~1\AppData\Local\Temp\calibre_e8t66c\yiy71r.epub
Parsing all content...
Parsing OEBPS/Text/@public@vhost@g@gutenberg@html@files@14105@14105-0-3.txt.html ...
Parsing OEBPS/Text/@public@vhost@g@gutenberg@html@files@14105@14105-0-4.txt.html ...
Parsing OEBPS/Styles/pgepub.css ...
CSSStylesheet: CSSCharsetRule only allowed at beginning of stylesheet. [8:1: @charset ]
Parsing OEBPS/Text/@public@vhost@g@gutenberg@html@files@14105@14105-0-5.txt.html ...
Parsing OEBPS/Text/@public@vhost@g@gutenberg@html@files@14105@14105-0-0.txt.html ...
Parsing OEBPS/Text/@public@vhost@g@gutenberg@html@files@14105@14105-0-1.txt.html ...
Parsing OEBPS/Text/@public@vhost@g@gutenberg@html@files@14105@14105-0-2.txt.html ...
Reading TOC from NCX...
Merging user specified metadata...
Detecting structure...
Flattening CSS and remapping font sizes...
Source base font size is 12.00000pt
Removing fake margins...
Found 1067 items of level: p_1
p_1  left margin stats: Counter({u'0': 1063, u'0%': 4})
p_1  right margin stats: Counter({u'0': 1063, u'0%': 4})
Cleaning up manifest...
Trimming unused files from manifest...
Creating KePub Output...
Rescaling image from 1200x1600 to 512x684 cover.jpeg
Splitting markup on page breaks and flow limits, if any...
	Looking for large trees in OEBPS/Text/%40public%40vhost%40g%40gutenberg%40html%40files%4014105%4014105-0-3.txt.html...
	No large trees found
	Looking for large trees in OEBPS/Text/%40public%40vhost%40g%40gutenberg%40html%40files%4014105%4014105-0-4.txt.html...
	No large trees found
	Looking for large trees in OEBPS/Text/%40public%40vhost%40g%40gutenberg%40html%40files%4014105%4014105-0-5.txt.html...
	No large trees found
		Splitting on page-break at id=id00008
		Splitting on page-break at id=id00009
	Looking for large trees in OEBPS/Text/%40public%40vhost%40g%40gutenberg%40html%40files%4014105%4014105-0-0.txt.html...
	No large trees found
	Split into 2 parts
	Looking for large trees in OEBPS/Text/%40public%40vhost%40g%40gutenberg%40html%40files%4014105%4014105-0-1.txt.html...
	No large trees found
	Looking for large trees in OEBPS/Text/%40public%40vhost%40g%40gutenberg%40html%40files%4014105%4014105-0-2.txt.html...
	No large trees found
Copying file 'C:\Users\JRGEN~1\AppData\Local\Temp\calibre_e8t66c\otfhxm_KePubOutputPluginInfo' to 'C:\Users\JRGEN~1\AppData\Local\Temp\calibre_e8t66c\sq4tgq_epub_container' as 'plugininfo.kte'
{'extended_kepub_features': True, 'no-hyphens': False, 'clean_markup': True, 'replace_lang': True, 'smarten_punctuation': False, 'hyphenate': True}
KoboTouchExtended:common:modify_epub:Found cover image ID 'cover'
KoboTouchExtended:common:modify_epub:Setting cover-image property
Forcing cleanup for file OEBPS/Text/@public@vhost@g@gutenberg@html@files@14105@14105-0-0.txt_split_000.html
Forcing cleanup for file OEBPS/Text/@public@vhost@g@gutenberg@html@files@14105@14105-0-0.txt_split_001.html
Forcing cleanup for file OEBPS/Text/@public@vhost@g@gutenberg@html@files@14105@14105-0-1.txt.html
Forcing cleanup for file OEBPS/Text/@public@vhost@g@gutenberg@html@files@14105@14105-0-2.txt.html
Forcing cleanup for file OEBPS/Text/@public@vhost@g@gutenberg@html@files@14105@14105-0-3.txt.html
Forcing cleanup for file OEBPS/Text/@public@vhost@g@gutenberg@html@files@14105@14105-0-4.txt.html
Forcing cleanup for file OEBPS/Text/@public@vhost@g@gutenberg@html@files@14105@14105-0-5.txt.html
Forcing cleanup for file titlepage.xhtml
Cleaning markup for file OEBPS/Text/@public@vhost@g@gutenberg@html@files@14105@14105-0-0.txt_split_000.html
Cleaning markup for file OEBPS/Text/@public@vhost@g@gutenberg@html@files@14105@14105-0-0.txt_split_001.html
Cleaning markup for file OEBPS/Text/@public@vhost@g@gutenberg@html@files@14105@14105-0-1.txt.html
Cleaning markup for file OEBPS/Text/@public@vhost@g@gutenberg@html@files@14105@14105-0-2.txt.html
Cleaning markup for file OEBPS/Text/@public@vhost@g@gutenberg@html@files@14105@14105-0-3.txt.html
Cleaning markup for file OEBPS/Text/@public@vhost@g@gutenberg@html@files@14105@14105-0-4.txt.html
Cleaning markup for file OEBPS/Text/@public@vhost@g@gutenberg@html@files@14105@14105-0-5.txt.html
Cleaning markup for file titlepage.xhtml
Copying file 'C:\Users\JRGEN~1\AppData\Local\Temp\calibre_e8t66c\kepub_5nxgqf_hyphenate' to 'C:\Users\JRGEN~1\AppData\Local\Temp\calibre_e8t66c\sq4tgq_epub_container' as 'kte-css/hyphenation.css'
Adding reference to kte-css/hyphenation.css to file OEBPS/Text/@public@vhost@g@gutenberg@html@files@14105@14105-0-0.txt_split_000.html
C:\Program Files\Calibre2\pylib.zip\ntpath.py:532: UnicodeWarning: Unicode unequal comparison failed to convert both arguments to Unicode - interpreting them as being unequal
Python function terminated unexpectedly
  All strings must be XML compatible: Unicode or ASCII, no NULL bytes or control characters (Error Code: 1)
Traceback (most recent call last):
  File "site.py", line 132, in main
  File "site.py", line 109, in run_entry_point
  File "site-packages\calibre\utils\ipc\worker.py", line 195, in main
  File "site-packages\calibre\gui2\convert\gui_conversion.py", line 33, in gui_convert_override
  File "site-packages\calibre\gui2\convert\gui_conversion.py", line 26, in gui_convert
  File "site-packages\calibre\ebooks\conversion\plumber.py", line 1226, in run
  File "calibre_plugins.kepubout.conversion.kepub_output", line 131, in convert
  File "calibre_plugins.kepubout.common", line 103, in modify_epub
  File "calibre_plugins.kepubout.container", line 178, in add_content_file_reference
  File "lxml.etree.pyx", line 1445, in lxml.etree._Element.makeelement (src\lxml\lxml.etree.c:49848)
  File "apihelpers.pxi", line 133, in lxml.etree._makeElement (src\lxml\lxml.etree.c:14869)
  File "apihelpers.pxi", line 121, in lxml.etree._makeElement (src\lxml\lxml.etree.c:14748)
  File "apihelpers.pxi", line 268, in lxml.etree._initNodeAttributes (src\lxml\lxml.etree.c:16296)
  File "apihelpers.pxi", line 290, in lxml.etree._addAttributeToNode (src\lxml\lxml.etree.c:16701)
  File "apihelpers.pxi", line 1395, in lxml.etree._utf8 (src\lxml\lxml.etree.c:26485)
ValueError: All strings must be XML compatible: Unicode or ASCII, no NULL bytes or control characters

I have no idea what is wrong.