setup.py: add 'gui' extra. potentially build Qt icons files

[SomberNight]

Rotonen suggested on IRC that it would be nice to be able to just pip install from github and have a working installation with GUI; something like:

pip install -Ue git+https:/spesmilo/[email protected]#egg=electrum[fast,gui]

For this,

• a gui extra is added that contains pyqt5
• we try to build the icons_rc.py file if it's not present and if pyqt5 is installed

[Rotonen]

Tried with pip install -Ue git+https:/SomberNight/electrum.git@setuptools_pyrcc#egg=electrum[fast,gui] and it fails to find the icon file. It'll also need to add it to the package resources / MANIFEST.in upon the extra.

Additionally the old guard responded to me on distutils-sig about how to detect extras gracefully:
https://mail.python.org/mm3/archives/list/[email protected]/thread/Z3LLXCCWWFHNRIHQTVFSHSYEJYNXSVXX/#Z3LLXCCWWFHNRIHQTVFSHSYEJYNXSVXX

[Rotonen]

Seems one should have compiled it before sdist.read_manifest() kicks in, so it gets picked up along for the ride.

https:/pypa/setuptools/blob/0254a2fda8e8bd4f289d01e2179191e936517f04/setuptools/command/sdist.py#L180

So hook into sdist instead of install and compile the file before you run the original sdist.read_manifest().

[Rotonen]

Sorry for the noise, user error.

Running pip install -U git+https:/SomberNight/electrum.git@setuptools_pyrcc#egg=Electrum[fast,gui] works.

The -e flag for pip makes the egg editable, which runs develop instead of install.

https:/pypa/setuptools/blob/0254a2fda8e8bd4f289d01e2179191e936517f04/setuptools/command/develop.py#L109