To enforce password-based ssh auth (fallback from key-based ssh auth) when collecting logs from hypervisors, user needs to do following:

  $ engine-log-collector -k ""

Note that -k option always requires some value (empty string in this case), otherwise it fails with following message:

  error: -k option requires an argument

Current help text for -k option says:

  If a identity file is not supplied the program will prompt for a password.

From above help text, it's not really obvious that user needs to specify empty string to enforce password-based ssh auth.

I suggest one of following (just ideas):

a, improve --help and man page documentation for -k option, for example:
   Provide empty string to make program prompt for a password.

b, introduce new option as shorthand for -k "", for example:
   $ engine-log-collector --use-pw-auth