Project path can't have umlauts in it. If it has, paths to footprints is not readable to KiCAD

Tested with Kubuntu 21.04 and KiCAD, affecting both the release and nightly

Version: 5.99.0-unknown-fdcc49d3ee~128~ubuntu21.04.1, release build

Libraries:
	wxWidgets 3.0.5
	libcurl/7.74.0 OpenSSL/1.1.1j zlib/1.2.11 brotli/1.0.9 libidn2/2.3.0 libpsl/0.21.0 (+libidn2/2.3.0) libssh/0.9.5/openssl/zlib nghttp2/1.43.0 librtmp/2.3

Platform: Linux 5.12.7-051207-lowlatency x86_64, 64 bit, Little endian, wxGTK, KDE, x11

Build Info:
	Date: May 28 2021 08:42:12
	wxWidgets: 3.0.5 (wchar_t,wx containers,compatible with 2.8) GTK+ 3.24
	Boost: 1.74.0
	OCC: 7.5.1
	Curl: 7.74.0
	ngspice: 34
	Compiler: GCC 10.3.0 with C++ ABI 1014

Build settings:
	KICAD_SCRIPTING=ON
	KICAD_SCRIPTING_MODULES=ON
	KICAD_SCRIPTING_PYTHON3=ON
	KICAD_SCRIPTING_WXPYTHON=ON
	KICAD_SCRIPTING_WXPYTHON_PHOENIX=ON
	KICAD_SCRIPTING_ACTION_MENU=ON
	KICAD_USE_OCC=ON
	KICAD_SPICE=ON

See https://forum.kicad.info/t/cant-create-footprint-in-5-1-or-nightly/29057/29 for screenshots and animated gifs.

To test, simply put your project folder (with a local footprint lib) into a folder /umläut/ and open it. You will get a warning on opening that the path to the local footprint library is not working.