Check, that SCons is started with Python 2.7 32-bit and warn the user…

… if not. (#8926)

* Ensure, that SCons is started with Python 2.7 32-bit fail otherwise. Fix for #7095

* Improve readability of the displayed message.

* Review actions

* Review actions.

scons.py

@@ -3,6 +3,19 @@
 
 import sys
 import os
+import platform
+# Variables for storing required version of Python, and the version which is used to run this script.
+requiredPythonMajor ="2"
+requiredPythonMinor = "7"
+requiredPythonArchitecture = "32bit"
+installedPythonMajor = str(sys.version_info.major)
+installedPythonMinor = str(sys.version_info.minor)
+installedPythonArchitecture = platform.architecture()[0]
+# Ensure, that we are running with required version of Python, otherwise inform the user and exit.
+if installedPythonArchitecture != requiredPythonArchitecture or installedPythonMajor != requiredPythonMajor or installedPythonMinor != requiredPythonMinor:
+	print("This script is started with Python %s.%s %s, however to build NVDA you have to use Python %s.%s %s." %(installedPythonMajor, installedPythonMinor, installedPythonArchitecture, requiredPythonMajor, requiredPythonMinor, requiredPythonArchitecture))
+	print("Please install the needed version of Python and launch SCons again, or if you have mulltiple versions of Python installed start this script with required version explicitly.")
+	sys.exit(1)
 sys.path.append(os.path.abspath(
 	os.path.join(__file__, "..", "source")))
 import sourceEnv