Perform a check on the Python version on startup. Refs #1592

Now only Python versions with matching major/minor numbers will be able
to import mantid.

Code/Mantid/Framework/PythonInterface/mantid/CMakeLists.txt

@@ -69,6 +69,15 @@ set ( PY_FILES
 
 copy_python_files_to_dir ( "${PY_FILES}" ${CMAKE_CURRENT_SOURCE_DIR} ${OUTPUT_DIR} 
                            PYTHON_PKGROOT_INSTALL_FILES )
+# Generate the version module
+set ( VERSION_PY pyversion )
+# Build version
+configure_file ( ${CMAKE_CURRENT_SOURCE_DIR}/${VERSION_PY}.py.in ${CMAKE_CURRENT_BINARY_DIR}/${VERSION_PY}.py )
+# Copy py to build directory, taking care of multi-config (MSVC) builds
+copy_python_files_to_dir ( ${VERSION_PY}.py ${CMAKE_CURRENT_BINARY_DIR} ${OUTPUT_DIR}
+                           PYTHON_PKGROOT_INSTALL_FILES )
+# Package version
+configure_file ( ${CMAKE_CURRENT_SOURCE_DIR}/${VERSION_PY}.py.in ${CMAKE_CURRENT_BINARY_DIR}/${VERSION_PY}.install.py )
 
 if ( MSVC )
   # On windows copy over the python wrapper to the build directory (hang it off kernel build)
@@ -102,3 +111,7 @@ set_property ( TARGET PythonInterface PROPERTY FOLDER "MantidFramework/Python" )
 
 # Pure Python files 
 install ( FILES ${PY_FILES} DESTINATION ${BIN_DIR}/mantid )
+# version.py that will overwrite the ones from the built target
+install ( FILES ${CMAKE_CURRENT_BINARY_DIR}/${VERSION_PY}.install.py DESTINATION
+          ${BIN_DIR}/mantid RENAME ${VERSION_PY}.py )
+

Code/Mantid/Framework/PythonInterface/mantid/__init__.py

@@ -16,6 +16,10 @@
       Implementing Algorithms, Virtual Instrument Geometry. 
 
 """
+###############################################################################
+# Check the current Python version is correct
+###############################################################################
+import pyversion
 
 ###############################################################################
 # Define the api version

Code/Mantid/Framework/PythonInterface/mantid/pyversion.py.in

@@ -0,0 +1,19 @@
+"""
+    Checks that the running version of Python is compatible with the version of
+    Python that Mantid was built with.
+"""
+import sys
+
+# Define the target major.minor version (i.e. the one mantid was built against)
+TARGET_VERSION="@PYTHON_VERSION_MAJOR@.@PYTHON_VERSION_MINOR@"
+
+_vers_info = sys.version_info
+_running_vers = "%d.%d" % (_vers_info[0],_vers_info[1])
+if _running_vers != TARGET_VERSION:
+    message = \
+"""Python version mismatch, cannot continue.
+Mantid was built against version '%s' but you are running version '%s'. These versions
+must match.
+"""
+    raise ImportError(message % (TARGET_VERSION, _running_vers))
+