Revert "Switch hard error to a WARNING for kernel version check"

This reverts commit fd06dcd.

The revert is not to make it a hard error again, this revert is needed
to revert cleanly the commit that added this as an error in the first
place.

Signed-off-by: Rodrigo Campos <[email protected]>

Author: rata

pkg/kubelet/kubelet_pods.go

@@ -138,8 +138,9 @@ func (kl *Kubelet) getKubeletMappings() (uint32, uint32, error) {
 				features.UserNamespacesSupport, err)
 		}
 		if kernelVersion != nil && !kernelVersion.AtLeast(version.MustParseGeneric(utilkernel.UserNamespacesSupportKernelVersion)) {
-			klog.InfoS("WARNING: the kernel version is incompatible with the feature gate, which needs as a minimum kernel version",
-				"kernelVersion", kernelVersion, "feature", features.UserNamespacesSupport, "minKernelVersion", utilkernel.UserNamespacesSupportKernelVersion)
+			return 0, 0, fmt.Errorf(
+				"the kernel version (%s) is incompatible with the %s feature gate, which needs %s as a minimum kernel version",
+				kernelVersion, features.UserNamespacesSupport, utilkernel.UserNamespacesSupportKernelVersion)
 		}
 	}