Setup

  $ pushd "$TESTDIR" > /dev/null
  $ source _setup.sh

Try to filter using only metadata without a sequence index.
This should fail because the requested filters rely on sequence information.

  $ ${AUGUR} filter \
  >  --metadata filter/data/metadata.tsv \
  >  --min-length 10000 \
  >  --output-strains "$TMP/filtered_strains.txt" > /dev/null
  ERROR: You need to provide a sequence index or sequences to filter on sequence-specific information.
  [2]
