couldn't find python during fallback on custom build of shaderc-sys v0.6.1

[rhlee1121]

This appears to be related to other issues (at least #1276 and #1258).

Nothing like a new computer to find requirements...

log snippet:

Compiling backtrace v0.3.44 error: failed to run custom build command for shaderc-sys v0.6.1

Caused by: process didn't exit successfully: C:\Users\Bob\Documents\Development\conrod\target\debug\build\shaderc-sys-b8c7453332ae1b42\build-script-build (exit code: 101) --- stdout cargo:warning=System installed library not found. Falling back to build from source

--- stderr thread 'main' panicked at '

couldn't find required command: "python"

', C:\Users\Bob.cargo\registry\src\github.com-1ecc6299db9ec823\shaderc-sys-0.6.1\build\cmd_finder.rs:50:13 note: run with RUST_BACKTRACE=1 environment variable to display a backtrace.

warning: build failed, waiting for other jobs to finish... error: build failed

[rhlee1121]

installing python leads to couldn't find ninja so now this has merged with #1258.

I won't close this as you still need to note python in the docs.