Bug#896295: python3-keras: keras fails to import

[Helmut Grohne]

Package: python3-keras
Version: 2.1.5-2
Severity: serious
User: helmutg at debian.org
Usertags: python-import

After installing python3-keras importing the module keras
into a python interpreter fails with the following error:

Using TensorFlow backend.
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/lib/python3/dist-packages/keras/__init__.py", line 3, in <module>
    from . import utils
  File "/usr/lib/python3/dist-packages/keras/utils/__init__.py", line 6, in <module>
    from . import conv_utils
  File "/usr/lib/python3/dist-packages/keras/utils/conv_utils.py", line 9, in <module>
    from .. import backend as K
  File "/usr/lib/python3/dist-packages/keras/backend/__init__.py", line 84, in <module>
    from .tensorflow_backend import *
  File "/usr/lib/python3/dist-packages/keras/backend/tensorflow_backend.py", line 5, in <module>
    import tensorflow as tf
ModuleNotFoundError: No module named 'tensorflow'

The vast majority of import failures is attributed to missing dependencies.
Often times that manifests as an ImportError or ModuleNotFoundError.
Typically, dependencies should be inserted by dh-python via ${python:Depends}
or ${python3:Depends}. Thus a missing dependency can be caused by incomplete
install_requires in setup.py. Sometimes a missing dependency of a dependency
is the cause, in such cases this bug should be reassigned.

Helmut