deactivate tests in test/unit/bio/sequence using chi2 These tests using randomness fail from time to time (1% of failure). They need to be disabled not to create false positive FTBFS.
ensure that Bio::RestrictionEnzyme::CutSymbol is defined in tests loading bio/utils/restriction_enzyme/cut_symbol.rb is not enough. bio/utils/restriction_enzyme.rb loads automatically cut_symbol.rb if called.
