I got that warning massage after upgrade to Spyder 5.0.0
"You have missing dependencies!
# Mandatory:
spyder_kernels>=2.0.1,<2.1.0 : 2.0.1 (NOK)"
the warning message may be misleading and unnecessary. I checked, and I have spyder_kernels 2.0.1 installed. The requirement is that the installed version needs to be greater than or equal to 2.01 and less than or equal to 2.1.0 — which mine is.
The issue is known and it will be fixed soon. Spyder isn't actually missing the dependency. It only thinks so. You can safely ignore the warning