[Matplotlib-users] failed experiment with tight_layout

[Neal B. <ndb...@gm...>]

/usr/lib64/python2.7/site-packages/matplotlib/tight_layout.py:225: UserWarning: 
tight_layout : falling back to Agg renderer
  warnings.warn("tight_layout : falling back to Agg renderer")
Traceback (most recent call last):
  File "./plot_stuff2.py", line 10, in <module>
    plt.tight_layout()
  File "/usr/lib64/python2.7/site-packages/matplotlib/pyplot.py", line 1255, in 
tight_layout
    fig.tight_layout(pad=pad, h_pad=h_pad, w_pad=w_pad, rect=rect)
  File "/usr/lib64/python2.7/site-packages/matplotlib/figure.py", line 1605, in 
tight_layout
    rect=rect)
  File "/usr/lib64/python2.7/site-packages/matplotlib/tight_layout.py", line 
325, in get_tight_layout_figure
    max_nrows = max(nrows_list)
ValueError: max() arg is an empty sequence

The plotting script is quite long and complex, so I won't post it, but it 
begins:

#!/usr/bin/python
import matplotlib as mpl
mpl.use ('pdf')

import matplotlib.pyplot as plt
plt.tight_layout()


It produces multipage-pdf using
from matplotlib.backends.backend_pdf import PdfPages

It works without plt.tight_layout().  Any clues what I did wrong here?