pep8 ftbfs in 18.04 LTS

according to
http://people.canonical.com/~doko/ftbfs-report/test-rebuild-20181222-bionic.html

pep8 ftbfs.

======================================================================
FAIL: test_checkers_testsuite (testsuite.test_all.Pep8TestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/<<PKGBUILDDIR>>/testsuite/test_all.py", line 37, in test_checkers_testsuite
    msg='%s failure(s)' % report.total_errors)
AssertionError: 7 is not false : 7 failure(s)

----------------------------------------------------------------------
Ran 30 tests in 1.194s

FAILED (failures=1)
Test failed: <unittest.runner.TextTestResult run=30 errors=0 failures=1>
error: Test failed: <unittest.runner.TextTestResult run=30 errors=0 failures=1>
debian/rules:26: recipe for target 'override_dh_auto_test' failed
make[1]: *** [override_dh_auto_test] Error 1
make[1]: Leaving directory '/<<PKGBUILDDIR>>'
debian/rules:10: recipe for target 'build' failed
make: *** [build] Error 2