Log Message:
py-fonttools: updated to 3.37.3

3.37.3:
- The previous release accidentally changed several files from Unix to DOS
  line-endings. Fix that.

3.37.2:
- [varLib] Temporarily revert the fix to load_masters(), which caused a
  crash in interpolate_layout() when deepcopy-ing OTFs.

3.37.1:
- [varLib] load_masters() now actually assigns the fonts it loads to the
  source.font attributes.
- [varLib] Fixed an MVAR table generation crash when sparse masters were
  involved.
- [voltLib] parse_coverage_() returns a tuple instead of an ast.Enum.
- [feaLib] A MarkClassDefinition inside a block is no longer doubly indented
  compared to the rest of the block.

3.37.0:
- [svgLib] Added support for converting elliptical arcs to cubic bezier curves
- [py23] Added backport for math.isfinite.
- [varLib] Apply HIDDEN flag to fvar axis if designspace axis has attribute
  hidden=1.
- Fixed "DeprecationWarning: invalid escape sequence" in Python 3.7.
- [voltLib] Fixed parsing glyph groups. Distinguish different PROCESS_MARKS.
  Accept COMPONENT glyph type.
- [feaLib] Distinguish missing value and explicit <NULL> for PairPos2
  format A. Round-trip useExtension keyword. Implemented
  ValueRecord.asFea method.
- [subset] Insert empty widths into hdmx when retaining gids