Issue with EpubHTML and uid

[Finkkbeiner]

Hi,

When creating a chapter using a special uid like that:
chap = epub.EpubHtml(title=chap_title, file_name=(delete_spaces(chap_title) + '.xhtml'), lang='en', uid=_uid+i)

I get the following error:

File "src/lxml/etree.pyx", line 3153, in lxml.etree.SubElement
  File "src/lxml/apihelpers.pxi", line 199, in lxml.etree._makeSubElement
  File "src/lxml/apihelpers.pxi", line 194, in lxml.etree._makeSubElement
  File "src/lxml/apihelpers.pxi", line 324, in lxml.etree._initNodeAttributes
  File "src/lxml/apihelpers.pxi", line 335, in lxml.etree._addAttributeToNode
  File "src/lxml/apihelpers.pxi", line 1539, in lxml.etree._utf8
TypeError: Argument must be bytes or unicode, got 'int'

Any idea why?

[aerkalov]

I would assume uid is a number and not a string.