Handles the case where the documentation should be built from a JSBSi…

…m module installed with `pip`.

If `cmake` is called but the module `_jsbsim` is not built, then Sphinx complains because the build directory contains an incomplete `jsbsim` module.

This commit works around that situation by allowing Sphinx to use a version of JSBSim that has been globally installed (with `pip` for instance) rather than the half-baked version that may reside in `build/tests`.

The purpose of this commit is to allow building the Python docs with a JSBSim module that has been installed by `pip`. This saves an additional complete build of the Python module when releasing JSBSim with our CI/CD workflow in GitHub.

doc/python/sphinx/conf.py.in

@@ -16,6 +16,14 @@ import sys
 
 sys.path.insert(0, '${CMAKE_BINARY_DIR}/tests')
 
+try:
+    import jsbsim._jsbsim
+except ModuleNotFoundError:
+    # If the JSBSim module cannot be loaded from the `tests` folder then
+    # restore `sys.path` to its inital value and use the globally installed
+    # JSBSim module, if there is one.
+    sys.path = sys.path[1:]
+
 # -- Project information -----------------------------------------------------
 
 project = u'JSBSim'