Remove pure-python exporter (#543)

This exporter generated a single-file standalone python script that could
simulate the exported model without requiring PySB itself (or Perl or BNG).
This exporter is very difficult to keep updated, and these days it's much
easier to get a working PySB environment with all of its dependencies.

pysb/export/__init__.py

@@ -21,7 +21,6 @@
 - ``kappa``
 - ``potterswheel``
 - ``sbml``
-- ``python``
 - ``pysb_flat``
 - ``mathematica``
 - ``matlab``
@@ -70,7 +69,6 @@
    bngl
    bng_net
    kappa
-   python
    pysb_flat
    stochkit
    json
@@ -130,7 +128,6 @@ def export(self):
         'kappa': 'KappaExporter',
         'potterswheel': 'PottersWheelExporter',
         'sbml': 'SbmlExporter',
-        'python': 'PythonExporter',
         'pysb_flat': 'PysbFlatExporter',
         'mathematica': 'MathematicaExporter',
         'matlab': 'MatlabExporter',

pysb/tests/test_exporters.py

@@ -67,10 +67,7 @@ def check_convert(model, format):
             raise
 
     if exported_file is not None:
-        if format == 'python':
-            # linspace arguments picked to avoid VODE warning
-            exec(exported_file + 'Model().simulate(tspan=numpy.linspace(0,1,501))\n', {'numpy': np})
-        elif format == 'pysb_flat':
+        if format == 'pysb_flat':
             exec(exported_file, {'__name__': model.name})
         elif format == 'sbml':
             # Skip the simulation comparison if roadrunner not available