maxima crashes if using plot in absence of gnuplot

[lftabera]

using maxima.plot needs gnuplot installed, either in the PATH or as an spkg.

In the absence of gnuplot, maxima.plot should send an error messages. It crashes instead.

(Ensure that you do not have gnuplot installed).

sage:  maxima.plot2d('sin(x)','[x,-5,5]')
....
EOF: End Of File (EOF) in read_nonblocking(). Exception style platform.
...
sage:

If you try again the same command

sage:  maxima.plot2d('sin(x)','[x,-5,5]')
Maxima crashed -- automatically restarting.
Exception RuntimeError: 'maximum recursion depth exceeded in __subclasscheck__' in <type 'exceptions.RuntimeError'> ignored
Exception RuntimeError: RuntimeError('maximum recursion depth exceeded in cmp',) in Exception RuntimeError: 'maximum recursion depth exceeded in __subclasscheck__' in <type 'exceptions.RuntimeError'> ignored
 ignored

And goes on with RuntimeError? endlessly, you have to kill sage to stop it.

With gnuplot installed everything goes smooth.

[lftabera]

I cannot reproduce the error with sage 4.7.1, now it catches a maxima error.

However, I have no idea how to add a doctest to this issue.

[rws]

Confirmed with the sage-6.2 binary installation.