matplotlib change?

[Michael F. Stemper]

I have some scripts running as cronjobs that capture the status
of some long-term processes and then periodically plot the data.
The box where they normally run went down yesterday for some
unknown reason, so I ran them manually on another box so that
others on the project could continue to watch progress.

I was surprised to see that the lines on the plot no longer went
all of the way to its border. Investigating showed me that this
is box-dependent.

Samples showing the difference:

good
  <http://www.math.wisc.edu/~mstemper2/Math/CharTabComp/Example12.png>

bad
  <http://www.math.wisc.edu/~mstemper2/Math/CharTabComp/Example13.png>

The names of the differing plots are based on the fact that one
was done on a box with python 2.7.12 and one with python 2.7.13.
(Note that the 2.7.12 box is running Ubuntu, while the 2.7.13 box
is running straight Debian.)

Is it likely that the difference in plots due to something that
changed in matplotlib between 2.7.12 and 2.7.13? If so, is there
some argument that I could specify in one of the functions to
prevent this padding/margin/waste? Is there a separate function
to call?

If the difference isn't due to a change in matplotlib, would it be
something OS-dependent? How can I track it down?

Thanks for any suggestions.

Appendix: Functions currently called

import matplotlib.pyplot as plt
plt.figure()
plt.plot()
plt.gca().xaxis.set_major_formatter()
plt.gca().xaxis.set_major_locator()
plt.legend()
plt.ylabel()
plt.savefig()

-- 
Michael F. Stemper
I feel more like I do now than I did when I came in.