I am experiencing this same issue on Fedora 29 after installing the Krita snap. It is using core18 also.
krita: execl failed: No such file or directory child exited with status 1
snap 2.37.2-1.fc29 snapd 2.37.2-1.fc29 series 16 fedora 29 kernel 4.20.8-200.fc29.x86_64
core18 18 719 stable krita 4.1.7.101 44 stable
I am experiencing this same issue on Fedora 29 after installing the Krita snap. It is using core18 also.
krita:
execl failed: No such file or directory
child exited with status 1
snap 2.37.2-1.fc29 200.fc29. x86_64
snapd 2.37.2-1.fc29
series 16
fedora 29
kernel 4.20.8-
core18 18 719 stable
krita 4.1.7.101 44 stable