Bug#1096223: python-escript: FTBFS: ImportError: cannot import name 'griddata' from 'matplotlib.mlab' (/usr/lib/python3/dist-packages/matplotlib/mlab.py)

[Adrian Bunk]

Control: retitle -1 python-escript FTBFS with NumPy 2

On Mon, Feb 17, 2025 at 05:23:04PM +0100, Lucas Nussbaum wrote:
> Source: python-escript
> Version: 5.6-10
> Severity: serious
> Justification: FTBFS
>...
> > Found boost/python/numpy.hpp. Building with boost numpy support.
> > Checking for C++ header file numpy/ndarrayobject.h... no
> > Checking for C++ library cppunit... yes
> > Checking for C++ library netcdf_c++4... yes
> > Checking for C++ library umfpack... yes
> > Checking for C++ library siloh5... yes
> > Checking for C++ library mpi... yes
> > Checking for C++ library boost_iostreams... yes
> > Matplotlib created a temporary cache directory at /tmp/matplotlib-b4glr_xd because the default path (/sbuild-nonexistent/.config/matplotlib) is not a writable directory; it is highly recommended to set the MPLCONFIGDIR environment variable to a writable directory, in particular to speed up the import of Matplotlib and to better support multiprocessing.
> > Traceback (most recent call last):
> >   File "<string>", line 1, in <module>
> >     from __future__ import print_function;import matplotlib;print(matplotlib.__version__);from matplotlib.mlab import griddata;print("1")
> >                                                                                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > ImportError: cannot import name 'griddata' from 'matplotlib.mlab' (/usr/lib/python3/dist-packages/matplotlib/mlab.py)
>...

I think this is a red herring, this message is already in successful builds:
https://buildd.debian.org/status/fetch.php?pkg=python-escript&arch=amd64&ver=5.6-10%2Bb1&stamp=1736264725&raw=0

The build started to fail with NumPy 2, and the
  Checking for C++ header file numpy/ndarrayobject.h... no
might be part of the problem (it was yes with NumPy 1).

cu
Adrian