$ tox -re pypy3
...
pypy3: commands[1]> sphinx-build -b doctest -d /home/tseaver/projects/Zope/Z3/zope.i18nmessageid/.tox/pypy3/.cache/doctrees docs /home/tseaver/projects/Zope/Z3/zope.i18nmessageid/.tox/pypy3/.cache/doctest
...
running tests...

Document: narr
--------------
**********************************************************************
File "narr.rst", line 96, in default
Failed example:
    robot.domain = "planetexpress"
Expected:
    Traceback (most recent call last):
    ...
    AttributeError: readonly attribute
Got:
    Traceback (most recent call last):
      File "/opt/pypy3.10-v7.3.16-linux64/lib/pypy3.10/doctest.py", line 1352, in __run
        exec(compile(example.source, filename, "single",
      File "<doctest default[0]>", line 1, in <module>
        robot.domain = "planetexpress"
      File "/home/tseaver/projects/Zope/Z3/zope.i18nmessageid/src/zope/i18nmessageid/message.py", line 79, in __setattr__
        raise TypeError('readonly attribute')
    TypeError: readonly attribute
**********************************************************************
File "narr.rst", line 101, in default
Failed example:
    robot.default = u"${name} is not a robot."
Expected:
    Traceback (most recent call last):
    ...
    AttributeError: readonly attribute
Got:
    Traceback (most recent call last):
      File "/opt/pypy3.10-v7.3.16-linux64/lib/pypy3.10/doctest.py", line 1352, in __run
        exec(compile(example.source, filename, "single",
      File "<doctest default[1]>", line 1, in <module>
        robot.default = u"${name} is not a robot."
      File "/home/tseaver/projects/Zope/Z3/zope.i18nmessageid/src/zope/i18nmessageid/message.py", line 79, in __setattr__
        raise TypeError('readonly attribute')
    TypeError: readonly attribute
**********************************************************************
File "narr.rst", line 106, in default
Failed example:
    robot.mapping = {'name': 'Bender'}
Expected:
    Traceback (most recent call last):
    ...
    AttributeError: readonly attribute
Got:
    Traceback (most recent call last):
      File "/opt/pypy3.10-v7.3.16-linux64/lib/pypy3.10/doctest.py", line 1352, in __run
        exec(compile(example.source, filename, "single",
      File "<doctest default[2]>", line 1, in <module>
        robot.mapping = {'name': 'Bender'}
      File "/home/tseaver/projects/Zope/Z3/zope.i18nmessageid/src/zope/i18nmessageid/message.py", line 79, in __setattr__
        raise TypeError('readonly attribute')
    TypeError: readonly attribute
**********************************************************************
1 items had failures:
   3 of  35 in default
35 tests in 1 items.
32 passed and 3 failed.
***Test Failed*** 3 failures.

Doctest summary
===============
   35 tests
    3 failures in tests
    0 failures in setup code
    0 failures in cleanup code
build finished with problems, 1 warning.
pypy3: exit 1 (2.17 seconds) /home/tseaver/projects/Zope/Z3/zope.i18nmessageid> sphinx-build -b doctest -d /home/tseaver/projects/Zope/Z3/zope.i18nmessageid/.tox/pypy3/.cache/doctrees docs /home/tseaver/projects/Zope/Z3/zope.i18nmessageid/.tox/pypy3/.cache/doctest pid=94066
pypy3: FAIL ✖ in 7.6 seconds

Collecting zope.i18nmessageid
  Downloading zope.i18nmessageid-5.0.0.tar.gz (28 kB)
    ERROR: Command errored out with exit status 1:
     command: /home/travis/virtualenv/pypy3.6-7.1.1/bin/pypy3 -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-rd8qof6w/zope.i18nmessageid/setup.py'"'"'; __file__='"'"'/tmp/pip-install-rd8qof6w/zope.i18nmessageid/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' egg_info --egg-base /tmp/pip-install-rd8qof6w/zope.i18nmessageid/pip-egg-info
         cwd: /tmp/pip-install-rd8qof6w/zope.i18nmessageid/
    Complete output (5 lines):
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/tmp/pip-install-rd8qof6w/zope.i18nmessageid/setup.py", line 25, in <module>
        from setuptools import setup, find_packages, Extension, Feature
    ImportError: cannot import name 'Feature'
    ----------------------------------------
ERROR: Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.

      File "//pypy/site-packages/zope/app/apidoc/browser/preference.py", line 40, in __init__
        super(ApidocEditPreferenceGroup, self).__init__(context, request)
      File "//pypy/site-packages/zope/app/preference/browser.py", line 84, in __init__
        self.label = Message(pref_msg, mapping={u'name': name})
      File "//pypy/site-packages/zope/i18nmessageid/message.py", line 41, in __new__
        default = ustr.default[:] if default is _marker else default
    TypeError: 'NoneType' object is not subscriptable

$ pip install zope.i18nmessageid==5.1.0
ERROR: Could not find a version that satisfies the requirement zope.i18nmessageid==5.1.0 (from versions: 3.4dev-r73161, 3.4.0, 3.4.2, 3.4.3, 3.5.0, 3.5.1, 3.5.2, 3.5.3, 3.6.0, 3.6.1, 4.0.0, 4.0.1, 4.0.2, 4.0.3, 4.1.0, 4.2, 4.3, 4.3.1, 5.0.0, 5.0.1)
ERROR: No matching distribution found for zope.i18nmessageid==5.1.0

    msgid = _(u'foo', mapping = {})
    msgid.mapping['bar'] = something