Catch PrincipalOperationException when checking group membership.   - Required convoluted way of checking membership (see comments in code).   - Fixes #121   - Logs noisy error messages if the exception is caught and bugs the     user to fix the situation.
Catch PrincipalOperationException when checking group membership.
  - Required convoluted way of checking membership (see comments in code).
  - Fixes #121
  - Logs noisy error messages if the exception is caught and bugs the
    user to fix the situation.

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