When trying to convert a PDF to EPUB, the following error occurs:
File "/gnu/store/kz6bgqw9z7akj11zh20wkx14cgq0s3n2-calibre-3.35.0/lib/calibre/calibre/ebooks/pdf/pdftohtml.py", line 76, in pdftohtml
_('Could not find pdftohtml, check it is in your PATH'))
Hardcode pdftohtml binary path by patching pdftohtml.py.
* gnu/packages/ebook.scm (calibre)[arguments]: Patch pdftohtml.py in
'configure phase to set hardcode pdftohtml binary path.