epochs error message not surfaced with "snap refresh"

[Ian Johnson]

When trying to refresh from one branch of the network-manager snap to another one with an incompatible epoch, the following error message presented does not mention epochs at all:

$ sudo snap refresh network-manager --channel=1.10/candidate
error: snap "network-manager" is not available on 1.10/candidate but is available to install on the
       following channels:

       1.10/beta snap refresh --channel=1.10/beta network-manager
       1.10/edge snap refresh --channel=1.10/edge network-manager

       Get more information with 'snap info network-manager'.

If the device is unable to refresh due to epochs, this should be surfaced to the user when calling snap refresh.