Can't install matplotlib

[ghostlyghastly]

Removing the version number requirement for torch ( #274 ), I get the following:

Collecting matplotlib==2.1.0
  Using cached matplotlib-2.1.0.tar.gz (35.7 MB)
  Preparing metadata (setup.py) ... error
  error: subprocess-exited-with-error

  × python setup.py egg_info did not run successfully.
  │ exit code: 1
  ╰─> [69 lines of output]
      ============================================================================
      Edit setup.cfg to change the build options

      BUILDING MATPLOTLIB
                  matplotlib: yes [2.1.0]
                      python: yes [3.7.9 (tags/v3.7.9:13c94747c7, Aug 17 2020,
                              18:58:18) [MSC v.1900 64 bit (AMD64)]]
                    platform: yes [win32]

      REQUIRED DEPENDENCIES AND EXTENSIONS
                       numpy: yes [version 1.20.0]
                         six: yes [using six version 1.16.0]
                    dateutil: yes [using dateutil version 2.8.2]
      backports.functools_lru_cache: yes [Not required]
                subprocess32: yes [Not required]
                        pytz: yes [pytz was not found. pip/easy_install may
                              attempt to install it after matplotlib.]
                      cycler: yes [using cycler version 0.10.0]
                     tornado: yes [using tornado version 6.2]
                   pyparsing: yes [using pyparsing version 3.0.9]
                      libagg: yes [pkg-config information for 'libagg' could not
                              be found. Using local copy.]
                    freetype: no  [The C/C++ header for freetype
                              (freetype2\ft2build.h) could not be found.  You may
                              need to install the development package.]
                         png: no  [The C/C++ header for png (png.h) could not be
                              found.  You may need to install the development
                              package.]
                       qhull: yes [pkg-config information for 'libqhull' could not
                              be found. Using local copy.]

      OPTIONAL SUBPACKAGES
                 sample_data: yes [installing]
                    toolkits: yes [installing]
                       tests: no  [skipping due to configuration]
              toolkits_tests: no  [skipping due to configuration]

      OPTIONAL BACKEND EXTENSIONS
                      macosx: no  [Mac OS-X only]
                      qt5agg: yes [installing, Qt: 5.15.2, PyQt: 5.15.2; PySide2
                              not found]
                      qt4agg: no  [PySide not found; PyQt4 not found]
                     gtk3agg: no  [Requires pygobject to be installed.]
                   gtk3cairo: no  [Requires cairocffi or pycairo to be installed.]
                      gtkagg: no  [Requires pygtk]
                       tkagg: yes [installing; run-time loading from Python Tcl /
                              Tk]
                       wxagg: yes [installing, version 4.2.0]
                         gtk: no  [Requires pygtk]
                         agg: yes [installing]
                       cairo: no  [cairocffi or pycairo not found]
                   windowing: yes [installing]

      OPTIONAL LATEX DEPENDENCIES
                      dvipng: no
                 ghostscript: no
                       latex: no
                     pdftops: no

      OPTIONAL PACKAGE DATA
                        dlls: no  [skipping due to configuration]

      ============================================================================
                              * The following required packages can not be built:
                              * freetype, png * Please check http://gnuwin32.sourc
                              * eforge.net/packages/freetype.htm for instructions
                              * to install freetype * Please check http://gnuwin32
                              * .sourceforge.net/packages/libpng.htm for
                              * instructions to install png
      [end of output]

  note: This error originates from a subprocess, and is likely not a problem with pip.
error: metadata-generation-failed

× Encountered error while generating package metadata.
╰─> See above for output.

note: This is an issue with the package mentioned above, not pip.
hint: See above for details.

This is on windows. Only solution visible at https://stackoverflow.com/questions/39060669/python-matplotlib-install-issue-on-windows-7-for-freetype-png-packages is changing version.

Removing version number requirement, which seems to help.

Also,

pypng
freetype-py

are required but missing from requirements.txt