Index: llvm/utils/git-svn/git-llvm
===================================================================
--- llvm/utils/git-svn/git-llvm
+++ llvm/utils/git-svn/git-llvm
@@ -133,6 +133,11 @@
     return shell(['svn'] + list(cmd), cwd=cwd, stdin=kwargs.get('stdin', None),
                  ignore_errors=kwargs.get('ignore_errors', None))
 
+def exists(cmd):
+    for path in os.environ["PATH"].split(os.pathsep):
+        if os.access(os.path.join(path, cmd), os.X_OK):
+            return True
+    return False
 
 def get_default_rev_range():
     # Get the branch tracked by the current branch, as set by
@@ -309,6 +314,11 @@
 
 
 if __name__ == '__main__':
+    if not exists('svn'):
+        die('error: git-llvm needs svn command, but svn is not installed.')
+    if subprocess.call('git svn --help > /dev/null 2>&1', shell=True) != 0:
+        die('error: "git svn" returns an error. Make sure you have installed git-svn.')
+
     argv = sys.argv[1:]
     p = argparse.ArgumentParser(
         prog='git llvm', formatter_class=argparse.RawDescriptionHelpFormatter,