message: Force-install tarpaulin.
diff: @@ -14,7 +14,7 @@ if [ "$TRAVIS_OS_NAME" = "osx" ] && [ "$GNUPLOT" = "yes" ]; then
  fi
  if [ "$COVERAGE" = "yes" ]; then
  - RUSTFLAGS="--cfg procmacro2_semver_exempt" cargo install cargo-tarpaulin
  + RUSTFLAGS="--cfg procmacro2_semver_exempt" cargo install cargo-tarpaulin --force
  fi
  if [ "$RUSTFMT" = "yes" ]; then
  