Insist on Cython prior to 3.0 (#1061)

Hopefully this is a quick-fix for #1060 - but a more permanent fix will be needed at some future point.

Now includes a work-around for #1062

Author: corranwebster

enable/__init__.py

@@ -43,11 +43,11 @@
     # Dependencies for PySide6
     "pyside6": ["pyface[pyside6]", "traitsui[pyside6]"],
     # Dependencies for PySide2
-    "pyside2": ["pyface[pyside2]", "traitsui[pyside2]"],
+    "pyside2": ["pyface[pyside2]", "traitsui[pyside2]", "pillow<10"],
     # Dependencies for PyQt6
     "pyqt6": ["pyface[pyqt6]", "traitsui[pyqt6]"],
     # Dependencies for PyQt5
-    "pyqt5": ["pyface[pyqt5]", "traitsui[pyqt5]"],
+    "pyqt5": ["pyface[pyqt5]", "traitsui[pyqt5]", "pillow<10"],
     # Dependencies for WxPython
     "wx": ["pyface[wx]", "traitsui[wx]"],
     # Dependencies for null backend (nothing right now)

pyproject.toml

@@ -1,5 +1,5 @@
 [build-system]
-requires = ["cython", "oldest-supported-numpy", "setuptools", "swig", "wheel"]
+requires = ["cython<3", "oldest-supported-numpy", "setuptools", "swig", "wheel"]
 build-backend = "setuptools.build_meta"
 
 [tool.cibuildwheel]