exception 'object has no attribute', make html fails

[qinohe]

Hi, building files fails in an ArchLinux systemd-nspawn container. (this used to work ;)
Building the same files with Debian systemd-nspawn succeeds.
After setting up this container(Arch) I get an exception 'object has no attribute', see log file below.

To Reproduce
setup an Arch systemd-nspawn container with the following commands:
$ pacstrap -i -c spawned base --ignore linux (spawned=container name!)
$ pacman -S git python-sphinx python-sphinx_rtd_theme python-pip make
$ pip install -r requirements.txt

Causing the problem
$ make html

Expected behavior
Docs being build

The project
https://github.com/opnsense/docs

Environment info

• OS: ArchLinux
• Python version:3.7.3
• Sphinx version: 2.1.2

Additional context
Log file:

Sphinx version: 2.1.2
Python version: 3.7.3 (CPython)
Docutils version: 0.14
Jinja2 version: 2.10.1
Last messages:
  writing output... [ 54%] manual/how-tos/haproxy_howtos
  writing output... [ 54%] manual/how-tos/insight
  writing output... [ 55%] manual/how-tos/installaws
  writing output... [ 55%] manual/how-tos/installazure
  writing output... [ 56%] manual/how-tos/installova
  writing output... [ 56%] manual/how-tos/interface_wireless_internal
  writing output... [ 56%] manual/how-tos/ips-feodo
  writing output... [ 57%] manual/how-tos/ips-geoip
  writing output... [ 57%] manual/how-tos/ips-sslfingerprint
  writing output... [ 58%] manual/how-tos/ipsec-road
Loaded extensions:
  sphinx.ext.mathjax (2.1.2) from /usr/lib/python3.7/site-packages/sphinx/ext/mathjax.py
  sphinxcontrib.applehelp (1.0.1) from /usr/lib/python3.7/site-packages/sphinxcontrib/applehelp/__init__.py
  sphinxcontrib.devhelp (1.0.1) from /usr/lib/python3.7/site-packages/sphinxcontrib/devhelp/__init__.py
  sphinxcontrib.htmlhelp (1.0.2) from /usr/lib/python3.7/site-packages/sphinxcontrib/htmlhelp/__init__.py
  sphinxcontrib.serializinghtml (1.1.3) from /usr/lib/python3.7/site-packages/sphinxcontrib/serializinghtml/__init__.py
  sphinxcontrib.qthelp (1.0.2) from /usr/lib/python3.7/site-packages/sphinxcontrib/qthelp/__init__.py
  alabaster (0.7.12) from /usr/lib/python3.7/site-packages/alabaster/__init__.py
  sphinx_sitemap (unknown version) from /usr/lib/python3.7/site-packages/sphinx_sitemap/__init__.py
  sphinx.ext.todo (2.1.2) from /usr/lib/python3.7/site-packages/sphinx/ext/todo.py
  sphinxcontrib.blockdiag (1.5.4) from /usr/lib/python3.7/site-packages/sphinxcontrib/blockdiag.py
  sphinxcontrib.nwdiag (1.0.4) from /usr/lib/python3.7/site-packages/sphinxcontrib/nwdiag.py
  sphinxcontrib.seqdiag (0.9.6) from /usr/lib/python3.7/site-packages/sphinxcontrib/seqdiag.py
  sphinxcontrib.actdiag (0.5.4) from /usr/lib/python3.7/site-packages/sphinxcontrib/actdiag.py
Traceback (most recent call last):
 File "/usr/lib/python3.7/site-packages/sphinxcontrib/nwdiag.py", line 208, in html_visit_nwdiag
   html_render_png(self, node)
 File "/usr/lib/python3.7/site-packages/sphinxcontrib/nwdiag.py", line 162, in html_render_png
   image.save()
 File "/usr/lib/python3.7/site-packages/blockdiag/drawer.py", line 187, in save
   return self.drawer.save(self.filename, size, self.format)
 File "/usr/lib/python3.7/site-packages/blockdiag/imagedraw/filters/linejump.py", line 181, in save
   self._run()
 File "/usr/lib/python3.7/site-packages/blockdiag/imagedraw/filters/linejump.py", line 108, in _run
   method(self.target, *args, **kwargs)
 File "/usr/lib/python3.7/site-packages/blockdiag/imagedraw/png.py", line 385, in image
   self.paste(image, (x, y))
 File "/usr/lib/python3.7/site-packages/blockdiag/imagedraw/png.py", line 137, in paste
   self._image.paste(image, pt, mask)
 File "/usr/lib/python3.7/site-packages/PIL/Image.py", line 1530, in paste
   self.im.paste(im, box)
TypeError: integer argument expected, got float

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
 File "/usr/lib/python3.7/site-packages/sphinx/cmd/build.py", line 284, in build_main
   app.build(args.force_all, filenames)
 File "/usr/lib/python3.7/site-packages/sphinx/application.py", line 345, in build
   self.builder.build_update()
 File "/usr/lib/python3.7/site-packages/sphinx/builders/__init__.py", line 319, in build_update
   len(to_build))
 File "/usr/lib/python3.7/site-packages/sphinx/builders/__init__.py", line 382, in build
   self.write(docnames, list(updated_docnames), method)
 File "/usr/lib/python3.7/site-packages/sphinx/builders/__init__.py", line 562, in write
   self._write_serial(sorted(docnames))
 File "/usr/lib/python3.7/site-packages/sphinx/builders/__init__.py", line 573, in _write_serial
   self.write_doc(docname, doctree)
 File "/usr/lib/python3.7/site-packages/sphinx/builders/html.py", line 644, in write_doc
   self.docwriter.write(doctree, destination)
 File "/usr/lib/python3.7/site-packages/docutils/writers/__init__.py", line 80, in write
   self.translate()
 File "/usr/lib/python3.7/site-packages/sphinx/writers/html.py", line 59, in translate
   self.document.walkabout(visitor)
 File "/usr/lib/python3.7/site-packages/docutils/nodes.py", line 174, in walkabout
   if child.walkabout(visitor):
 File "/usr/lib/python3.7/site-packages/docutils/nodes.py", line 174, in walkabout
   if child.walkabout(visitor):
 File "/usr/lib/python3.7/site-packages/docutils/nodes.py", line 174, in walkabout
   if child.walkabout(visitor):
 File "/usr/lib/python3.7/site-packages/docutils/nodes.py", line 166, in walkabout
   visitor.dispatch_visit(self)
 File "/usr/lib/python3.7/site-packages/docutils/nodes.py", line 1882, in dispatch_visit
   return method(node)
 File "/usr/lib/python3.7/site-packages/blockdiag/utils/rst/directives.py", line 54, in decorator
   return fn(*args)
 File "/usr/lib/python3.7/site-packages/sphinxcontrib/nwdiag.py", line 221, in html_visit_nwdiag
   self.builder.warn('dot code %r: %s' % (node['code'], str(exc)))
AttributeError: 'StandaloneHTMLBuilder' object has no attribute 'warn'

[qinohe]

Updating to:
python-3.7.4
docutils 0.15.2
Had no effect, same error.

[tk0miya]

Unfortunately, this is a bug of sphinxcontrib-nwdiag. So please report this into their project (it's me! But here is not appropriate place to fix it)

[qinohe]

Sure ;) and thanks for this beautiful project.