[why]
When the font does not have a PSweight string the font-patcher bugs.

[how]
Rewrite the code to be more robust against unexpected weight values.
Also make detected problems non-fatal.

Reported-by: František Hanzlík <frantisek_hanzlik@protonmail.com>
Signed-off-by: Fini Jastrow <ulf.fini.jastrow@desy.de>

[why]
When the weight check fails for some input the reason is not shown
correctly (i.e. not the string that actually failed).

[how]
Display exactly the failed string in the warning.

Signed-off-by: Fini Jastrow <ulf.fini.jastrow@desy.de>

[why]
Some PS weights have a dash in the weight, like 'Extra-Light' in
Iosevka. The parser can not parse it because it expects 'ExtraLight'.

[how]
Filter out all '-' and ' ' from the PS weight string before actually
parsing the string.

Signed-off-by: Fini Jastrow <ulf.fini.jastrow@desy.de>