Converted autogen doctests to Python syntax

[defeo]

Item 3 in #4

[defeo]

This one particularly bugs me. Why were we chdir'ing before?

[videlec]

autogen is not a valid Python module (you would have to modify the Python path). I do not know how to properly use doctest for it. Are you able to run the doctests?

[defeo]

All the doctests pass on my machine (both Py2 and Py3). I'm just trying to convince Travis to run them. I tried modifying sys.path, to no avail. I'd have to reproduce the problem on my machine, first.

[videlec]

I will try on mine...

[videlec]

I got

$ python tests/rundoctest.py 
Traceback (most recent call last):
  File "tests/rundoctest.py", line 6, in <module>
    import autogen
ModuleNotFoundError: No module named 'autogen'

which I believe is normal since autogen is not a Python module available from the Python path...

[defeo]

Finally! Test pass. The sys.path fix is a bit hacky. If you have a better idea, feel free to implement.

[videlec]

This is my only objection.

[videlec]

This line is dangerous! It will change the behavior of import cypari2... you would better first test cypari2 as it used to be and in a second time, go to the appropriate directory and doctest autogen.

[defeo]

Why would it change the behavior of import cypari2?

[videlec]

Because you have a cypari2 repository in ../

[videlec]

The current version of rundoctest is doctesting the installed cypari2.

[defeo]

os.chdir does not change the python module search path, and the search path for a script run with python script.py does not contain ..

The incriminated line would rather be the following one, that adds the cypari2 directory to sys.path. But it only adds that to the end of sys.path, so it does not take precedence over the installed cypari2.

[defeo]

autogen.generator needs to read cypari2/paridecl.pxd and cypari2/declinl.pxi in order to run doctests, so it fails if we do not chdir.

[defeo]

If I run python test/rundoctest.py in a freshly cloned repo without installing I get

Traceback (most recent call last):
  File "tests/rundoctest.py", line 5, in <module>
    import cypari2
ModuleNotFoundError: No module named 'cypari2'

Again, that's because . is not in sys.path if you run python script.py.

Isn't that enough for an error message? Why would you want a tailored message?

[videlec]

Ok right. The message is good enough.

[videlec]

But you should at least replace .. by os.path.pardir that is more robust.

[defeo]

Agreed.

[videlec]

I would like

import cypari2

to be replaced by

try:
    import cypari2
except ImportError:
    raise ValueError('cypari2 must be installed in order to test it')

[defeo]

Done. If you're happy with it, feel free to merge.