AttributeError: 'Checker' object has no attribute 'blank_before'

[Nobuto Murata]

If python3-hacking package is installed, python3-flake8 always returns AttributeError: 'Checker' object has no attribute 'blank_before'.

$ cat foo.py
#!/usr/bin/python3

pass

$ python3 -m flake8 -vv foo.py
checking foo.py
pass
Traceback (most recent call last):
  File "/usr/lib/python3.4/runpy.py", line 170, in _run_module_as_main
    "__main__", mod_spec)
  File "/usr/lib/python3.4/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/usr/lib/python3/dist-packages/flake8/__main__.py", line 4, in <module>
    main()
  File "/usr/lib/python3/dist-packages/flake8/main.py", line 32, in main
    report = flake8_style.check_files()
  File "/usr/lib/python3/dist-packages/pep8.py", line 1624, in check_files
    runner(path)
  File "/usr/lib/python3/dist-packages/flake8/engine.py", line 83, in input_file
    return fchecker.check_all(expected=expected, line_offset=line_offset)
  File "/usr/lib/python3/dist-packages/pep8.py", line 1393, in check_all
    self.check_logical()
  File "/usr/lib/python3/dist-packages/pep8.py", line 1327, in check_logical
    for result in self.run_check(check, argument_names):
  File "/usr/lib/python3/dist-packages/pep8.py", line 1256, in run_check
    arguments.append(getattr(self, name))
AttributeError: 'Checker' object has no attribute 'blank_before'

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: python3-flake8 2.2.2-1ubuntu1
ProcVersionSignature: Ubuntu 3.19.0-7.7-generic 3.19.0
Uname: Linux 3.19.0-7-generic x86_64
ApportVersion: 2.16.2-0ubuntu1
Architecture: amd64
CurrentDesktop: Unity
Date: Sun Mar 8 15:15:00 2015
EcryptfsInUse: Yes
InstallationDate: Installed on 2015-02-28 (7 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Alpha amd64 (20150228)
SourcePackage: python-flake8
UpgradeStatus: No upgrade log present (probably fresh install)

[Hans Joachim Desserud (hjd)]

Thanks for taking your time to report this issue and help making Ubuntu better.

I was not able to reproduce this issue when I tested on an up-to-date Vivid system:
$ python3 -m flake8 -vv foo.py
checking foo.py
pass

Looks like the underlying problem occurs when it calls pep8, which version of pep8 do you have installed?

$ apt-cache policy python3-flake8
python3-flake8:
  Installed: 2.2.2-1ubuntu1
  Candidate: 2.2.2-1ubuntu1
  Version table:
 *** 2.2.2-1ubuntu1 0
        500 http://no.archive.ubuntu.com/ubuntu/ vivid/main amd64 Packages
        100 /var/lib/dpkg/status

$ apt-cache policy python3-pep8
python3-pep8:
  Installed: 1.5.7-2
  Candidate: 1.5.7-2
  Version table:
 *** 1.5.7-2 0
        500 http://no.archive.ubuntu.com/ubuntu/ vivid/main amd64 Packages
        100 /var/lib/dpkg/status

[Nobuto Murata (nobuto)]

Hi,
I've checked it again with a fresh LXC container of vivid. The issue is still reproducible with the same version as you posted.
python3-flake8: 2.2.2-1ubuntu1
python3-pep8: 1.5.7-2

Interestingly executing pep8 alone does not output any errors.

$ python3 -m pep8 -vv foo.py
checking foo.py
pass

$ python3 -m flake8 -vv foo.py
<the same traceback>

[Nobuto Murata (nobuto)]

ah, the traceback occurs only if python3-hacking package is installed.

[Hans Joachim Desserud (hjd)]

Thanks for investigating. After installing python3-hacking I get the same stack trace.

[Felipe Reyes (freyes)]

Hi,

I'm hitting this problem and started troubleshooting to find a root cause, and I found something I don't understand. This is the output I receive in a clean Vivid environment:

root@vivid:~# dpkg -l python3-pep8 pep8
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-====================-===============-===============-==============================================
ii pep8 1.5.7-2 all Python PEP 8 code style checker - python2
ii python3-pep8 1.5.7-2 all Python PEP 8 code style checker - python3
root@vivid:~# python -c "import pep8; print(pep8.__version__)"
1.5.7
root@vivid:~# python -c "import pep8; print(pep8.__file__)"
/usr/lib/python2.7/dist-packages/pep8.pyc
root@vivid:~# python3 -c "import pep8; print(pep8.__version__)"
1.4.6
root@vivid:~# python3 -c "import pep8; print(pep8.__file__)"
/usr/lib/python3/dist-packages/pep8.py

Why pep8 for python3 is version 1.4.6 while for python2 is 1.5.7?

Here is the output of "diff -u /usr/lib/python3/dist-packages/pep8.py /usr/lib/python2.7/dist-packages/pep8.py" (see attachment) which I would expect to be just a few lines (the shebang, maybe a timestamp and that's it), but it's not, files are completely different.

$ diffstat /tmp/py3-py2.diff
 pep8.py | 700 ++++++++++++++++++++++++++++++++++------------------------------
 1 file changed, 382 insertions(+), 318 deletions(-)

[Felipe Reyes (freyes)]

This bug is debian is related https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=788132 , I provided a patch to fix the issue in debian. Using the patched version I could run without problems the test cases provided by Nobuto

Basically a file is being added (build/lib/pep8.py) by the debian diff and that version seems to be a leftover from a previous version.

[Hans Joachim Desserud (hjd)]

Looks like the Debian bug resolved this issue. I'm no longer able to reproduce it with pep8 1.6.2-0.1 on Ubuntu 15.10 or later versions.