add python3 checks to avoid confusion from errors with python2.

build_files/cmake/cmake_consistency_check.py

@@ -22,6 +22,12 @@
 
 # <pep8 compliant>
 
+import sys
+if not sys.version.startswith("3"):
+    print("\nPython3.x needed, found %s.\nAborting!\n" %
+          sys.version.partition(" ")[0])
+    sys.exit(1)
+
 from cmake_consistency_check_config import IGNORE, UTF8_CHECK, SOURCE_DIR
 
 import os

build_files/cmake/project_info.py

@@ -44,7 +44,14 @@ __all__ = (
     "project_name_get"
 )
 
+
 import sys
+if not sys.version.startswith("3"):
+    print("\nPython3.x needed, found %s.\nAborting!\n" %
+          sys.version.partition(" ")[0])
+    sys.exit(1)
+
+
 import os
 from os.path import join, dirname, normpath, abspath, splitext, exists
 

build_files/cmake/project_source_info.py

@@ -25,6 +25,14 @@ __all__ = (
     "SOURCE_DIR",
     )
 
+
+import sys
+if not sys.version.startswith("3"):
+    print("\nPython3.x needed, found %s.\nAborting!\n" %
+          sys.version.partition(" ")[0])
+    sys.exit(1)
+
+
 import os
 from os.path import join, dirname, normpath, abspath