FindPython: migrate tests to RunCMake framework

Tests/RunCMake/FindPython/VirtualEnvOnly.cmake

@@ -0,0 +1,17 @@
+cmake_minimum_required(VERSION 3.15)
+
+#
+# Virtual environment is defined for python3
+# Trying to find a python2 using only virtual environment
+# It is expecting to fail if a virtual environment is active and to success otherwise.
+#
+set (Python2_FIND_VIRTUALENV ONLY)
+find_package (Python2 QUIET)
+
+if (PYTHON3_VIRTUAL_ENV AND Python2_FOUND)
+  message (FATAL_ERROR "Python2 unexpectedly found.")
+endif()
+
+if (NOT PYTHON3_VIRTUAL_ENV AND NOT Python2_FOUND)
+  message (FATAL_ERROR "Fail to find Python2.")
+endif()