The texture name itself is not too long, but the related $depth one is:
Warn: FinishShader Shader name textures/test-pngalpha_custom/test-grayscale8-alpha1_alpha$depth length longer than MAX_QPATH 64
Warn: FinishShader Shader name textures/test-pngalpha_custom/test-grayscale1-alpha8_alpha$depth length longer than MAX_QPATH 64
Warn: FinishShader Shader name textures/test-pngalpha_custom/test-grayscale1-alpha1_alpha$depth length longer than MAX_QPATH 64
The texture name itself is not too long, but the related
$depth
one is: