Bug#896254: python-sagenb: sagenb fails to import

[Helmut Grohne]

Package: python-sagenb
Version: 1.0.1+ds1-2
Severity: serious
User: helmutg at debian.org
Usertags: python-import

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

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/lib/python2.7/dist-packages/sagenb/__init__.py", line 3, in <module>
    from . import storage
  File "/usr/lib/python2.7/dist-packages/sagenb/storage/__init__.py", line 3, in <module>
    from .filesystem_storage import FilesystemDatastore
  File "/usr/lib/python2.7/dist-packages/sagenb/storage/filesystem_storage.py", line 54, in <module>
    from sage.misc.temporary_file import atomic_write
ImportError: No module named sage.misc.temporary_file

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