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This fixes an error 500 when trying to tally when no ballots have been
cast.

implement verification, at the end of all votes, of every ballot (smart ballot tracker) in the ballot box page

The name was conflicting with Pervasives.result.

The name was conflicting with Pervasives.Error.

Rationale: the mutex in Web_election was ineffective. Database
manipulations (and the mutex) have been moved to Web_persist; the rest
has been moved to Web_site.

# Conflicts:
#	tests/test_scenario_1.py