"Infelicity" while compiling sagetex documents

[Emmanuel Charpentier]

Something seems to have changed either in my Sage or my Python installation, but I can't diagnose it :

I wanted to compile (again) the sagetex documentation. Compiling sagetex.dtx was a breeze (pdflatex sagetex.dtx ; sage sagetex.sagetex.sage ; pdflatex sagetex.dtx).

pdflatex example.tex went OK. However, sage can't evaluate the resultatn example.sagetex.sage :

charpent@eee-ec:/usr/local/sage/local/share/texmf/tex/generic/sagetex$ sage example.sagetex.sage 

Processing Sage code for example.tex...

Inline formula 0

Inline formula 1

Inline formula 2

Inline formula 3

Code block begin...end

Inline formula 4

Inline formula 5

Inline formula 6

Code block begin...end

Inline formula 7

Inline formula 8

Code block begin...end

Inline formula 9

Inline formula 10

Code block begin...end

Inline formula 11

Code block begin...end

Inline formula 12

Initializing plots directory

Plot 0

Code block begin...end

Code block begin...end

Plot 1

Plot 2

Code block begin...end

Code block begin...end

Plot 3

Plot 4

Code block begin...end

Plot 5

Code block begin...

**** Error in Sage code on line 180 of example.tex! Traceback follows.

Traceback (most recent call last):

  File "example.sagetex.py", line 173, in <module>

    matrixprogram = matrix_plot(M,cmap='Greys')

  File "/home/charpent/sage-5.10/local/lib/python2.7/site-packages/sage/misc/decorators.py", line 456, in wrapper

    return func(*args, **kwds)

  File "/home/charpent/sage-5.10/local/lib/python2.7/site-packages/sage/misc/decorators.py", line 456, in wrapper

    return func(*args, **kwds)

  File "/home/charpent/sage-5.10/local/lib/python2.7/site-packages/sage/misc/decorators.py", line 534, in wrapper

    return func(*args, **options)

  File "/home/charpent/sage-5.10/local/lib/python2.7/site-packages/sage/plot/matrix_plot.py", line 457, in matrix_plot

    import scipy.sparse as scipysparse

ImportError: No module named scipy.sparse

**** Running Sage on example.sage failed! Fix example.tex and try again.

A bit of googling led me to  this, which inspired me to go to $SAGE_ROOT/local/lib/python and do ln -s site-packages/Ipithon/* . No success... Nor did sage PYTHONNOUSERSITE=yes example.sagetex.sage

Could some kind soul point me to the direction of my stupidity ?

Sincerely,