Auto-install Python Package

[varunagrawal]

New make python-install command to automatically install the python wrapper.

The installation flow is as simple as

cmake ..
make -j4
make python-install

The major update is that instead of copying all the build artifacts to a 3rd party location (e.g. /usr/loca/cython), we instead store the build artifacts under the cmake build/cython directory (with build tags getting added as postfixes by default).

Running make now builds all the wrapper artifacts directly and in place, removing the need to run make install.

The make python-install command then installs the build artifacts by running the setup.py making installation a one-line command. Since we no longer rely on make install, the make python-install command can directly handle all the dependencies.

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This change is 

[varunagrawal]

@jlblancoc I may need your help on this PR. I need to add corresponding python wrapper installation instructions in the cython/scripts/install.bat file for Windows and you are the expert on this.

[jlblancoc]

@jlblancoc I may need your help on this PR. I need to add corresponding python wrapper installation instructions in the cython/scripts/install.bat file for Windows and you are the expert on this.

Hmmm... what about a cmake script instead, so it's common to both Windows and Linux?

[varunagrawal]

I actually tried a cmake script first but running with superuser became problematic and it wouldn't work consistently.
However, I've actually learned some new tricks since then so let me try again.

[varunagrawal]

Okay that worked beautifully for me on Linux. Thank you @jlblancoc!

[varunagrawal]

This should be ready for review now.

[ProfFan]

@varunagrawal have you tried installing and test on all normal configurations (Debug, Release, RelWithDebInfo)?

[varunagrawal]

I tested with Release and Debug. Testing with RelWithDebugInfo now.

[varunagrawal]

@ProfFan @dellaert updated this PR and the description. This should satisfy all the requirements. 🙂

[dellaert]

I am now completely confused, and want to talk in person before merging. It seems a lot of work/confusion for something that was not a problem to begin with (at least for me) and will, when merged, impart confusion on existing users. I'm happy to be convinced otherwise, in person.

There seem to be a lot of unrelated changes in this PR as well (with the build suffixes etc) that make reviewing hard.

[varunagrawal]

Sure thing. Yeah this PR went through a lot of different cycles due to different requirements being pushed in at different times.

It wasn't a problem per se, but I have not been a fan of having to go into a separate directory just to install the wrapper to the python environment.

[dellaert]

@varunagrawal this is cython so we should either give up or put in 45.0.3. Please summarize what this PR now does.

[dellaert]

@varunagrawal this is the only PR left in 4.0.3

[varunagrawal]

This should still be useful for generating packages with the new Pybind11 wrapper.

Moreover, it has a good number of nice fixes to the setup.py and CMake files.

[ProfFan]

@varunagrawal I have implemented python-install in the pybind branch already (because in the pybind branch and possibly 4.1 make install will not copy the python files to the prefix, resulting in a much cleaner install).

I think this can be picked into 4.0.3 after branching out release_4.0.3

[dellaert]

This should still be useful for generating packages with the new Pybind11 wrapper.

Moreover, it has a good number of nice fixes to the setup.py and CMake files.

Please summarize what this PR now does.

[varunagrawal]

This PR

1. Gets rid of the install step for the python wrapper by building everything into the cython directory under the cmake build directory.
2. Adds a new make command python-install which generates the python package and installs it via python setup.py install.
3. Introduces a bunch of clean ups to the Cython Cmake files and the setup.py.in template file.

[dellaert]

OK, thanks! @ProfFan this seems identical to what you did in pybind. Please confirm or tell us how it is different, and what needs to change in this PR - if anything. It should be identical - no sense in changing gears twice in a month.

[ProfFan]

@dellaert Yes it is identical. I believe this could go into the release branch after branching out (since 4.1 will not have Cython stuff)

[dellaert]

@ProfFan can't we just merge into develop and then merge all recent changes from develop into the already existing 4.0.3 branch?

[ProfFan]

@dellaert Yes