Try python2 before python.

xb.bat

@@ -9,7 +9,7 @@ REM ============================================================================
 
 CALL :check_python
 IF %_RESULT% NEQ 0 (
-  ECHO ERROR:
+  ECHO.
   ECHO Python 2.7 must be installed and on PATH:
   ECHO https://www.python.org/ftp/python/2.7.9/python-2.7.9.msi
   GOTO :exit_error
@@ -20,7 +20,7 @@ REM ============================================================================
 REM Trampoline into xenia-build
 REM ============================================================================
 
-python xenia-build %*
+%PYTHON_EXE% xenia-build %*
 EXIT /b %ERRORLEVEL%
 
 
@@ -30,15 +30,32 @@ REM ============================================================================
 
 :check_python
 SETLOCAL
-1>NUL 2>NUL CMD /c where python
-IF %ERRORLEVEL% NEQ 0 (
+SET FOUND_PYTHON_EXE=""
+1>NUL 2>NUL CMD /c where python2
+IF NOT ERRORLEVEL 1 (
+  ECHO FOUND PYTHON 2
+  SET FOUND_PYTHON_EXE=python2
+)
+IF %FOUND_PYTHON_EXE% EQU "" (
+  1>NUL 2>NUL CMD /c where python
+  IF NOT ERRORLEVEL 1 (
+    SET FOUND_PYTHON_EXE=python
+  )
+)
+IF %FOUND_PYTHON_EXE% EQU "" (
+  ECHO ERROR: no Python executable found on PATH.
+  ECHO Make sure you can run 'python' or 'python2' in a Command Prompt.
   ENDLOCAL & SET _RESULT=1
   GOTO :eof
 )
-CMD /c python -c "import sys; sys.exit(1 if not sys.version_info[:2] == (2, 7) else 0)"
+CMD /C %FOUND_PYTHON_EXE% -c "import sys; sys.exit(1 if not sys.version_info[:2] == (2, 7) else 0)"
 IF %ERRORLEVEL% NEQ 0 (
+  ECHO ERROR: Python version mismatch - not 2.7
   ENDLOCAL & SET _RESULT=1
   GOTO :eof
 )
-ENDLOCAL & SET _RESULT=0
+ENDLOCAL & (
+  SET _RESULT=0
+  SET PYTHON_EXE=%FOUND_PYTHON_EXE%
+)
 GOTO :eof