PyInstaller fixes (need older scipy)

nanovna-saver.py

@@ -14,6 +14,7 @@
 #  You should have received a copy of the GNU General Public License
 #  along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
+import pkg_resources.py2_warn
 from NanoVNASaver.__main__ import main
 
 if __name__ == '__main__':

requirements.txt

@@ -1,4 +1,5 @@
-scipy
+scipy==1.4.1
+cython
 pyqt5
 pyserial
-numpy
+numpy

setup.py

@@ -42,6 +42,7 @@ setup(
         'pyserial',
         'PyQt5',
         'numpy',
-        'scipy'
+        'scipy<1.5',
+        'cython',
     ],
 )