Description of problem:
Using matplotlib-python with gtk backend, I've an error saying dvipng: command not found.

Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/matplotlib/backends/backend_gtk.py",
line 393, in expose_event
    self._render_figure(self._pixmap, w, h)
  File
"/usr/lib/python2.7/site-packages/matplotlib/backends/backend_gtkagg.py", line
75, in _render_figure
    FigureCanvasAgg.draw(self)
  File "/usr/lib/python2.7/site-packages/matplotlib/backends/backend_agg.py",
line 394, in draw
    self.figure.draw(self.renderer)
  File "/usr/lib/python2.7/site-packages/matplotlib/artist.py", line 55, in
draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/matplotlib/figure.py", line 798, in
draw
    func(*args)
  File "/usr/lib/python2.7/site-packages/matplotlib/artist.py", line 55, in
draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/matplotlib/axes.py", line 1934, in
draw
    a.draw(renderer)
  File "/usr/lib/python2.7/site-packages/matplotlib/artist.py", line 55, in
draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/matplotlib/axis.py", line 1017, in
draw
    tick.draw(renderer)
  File "/usr/lib/python2.7/site-packages/matplotlib/artist.py", line 55, in
draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/matplotlib/axis.py", line 234, in draw
    self.label1.draw(renderer)
  File "/usr/lib/python2.7/site-packages/matplotlib/artist.py", line 55, in
draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/matplotlib/text.py", line 567, in draw
    self._fontproperties, angle)
  File "/usr/lib/python2.7/site-packages/matplotlib/backends/backend_agg.py",
line 198, in draw_tex
    Z = texmanager.get_grey(s, size, self.dpi)
  File "/usr/lib/python2.7/site-packages/matplotlib/texmanager.py", line 513,
in get_grey
    pngfile = self.make_png(tex, fontsize, dpi)
  File "/usr/lib/python2.7/site-packages/matplotlib/texmanager.py", line 459,
in make_png
    \n\n'% dvifile + report)
RuntimeError: dvipng was not able to process the following file:
/root/.matplotlib/tex.cache/4e985473485b35b1b4ab262652c2c542.dvi
Here is the full report generated by dvipng:

Version-Release number of selected component (if applicable):
python-matplotlib-1.0.1-11.fc14.i686

How reproducible:
Always reproducible 

Steps to Reproduce:
1. plot a graph with mathplotlib using gtk backend.
2.
3.
  
Actual results:
RuntimeError: dvipng not found

Expected results:
No missing dependency on dvipng