Catch CalledProcessError exception in install script

This exception is not relevant to the install failure. Catch it and exit
with the status code returned by the build script.

install.py

@@ -22,15 +22,22 @@
 DIR_OF_OLD_LIBS = p.join( DIR_OF_THIS_SCRIPT, 'python' )
 
 
+def CheckCall( args, **kwargs ):
+  try:
+    subprocess.check_call( args, **kwargs )
+  except subprocess.CalledProcessError as error:
+    sys.exit( error.returncode )
+
+
 def Main():
   build_file = p.join( DIR_OF_THIS_SCRIPT, 'third_party', 'ycmd', 'build.py' )
 
   if not p.isfile( build_file ):
-    sys.exit( 'File ' + build_file + ' does not exist; you probably forgot '
-              'to run:\n\tgit submodule update --init --recursive\n\n' )
+    sys.exit(
+      'File {0} does not exist; you probably forgot to run:\n'
+      '\tgit submodule update --init --recursive\n'.format( build_file ) )
 
-  python_binary = sys.executable
-  subprocess.check_call( [ python_binary, build_file ] + sys.argv[1:] )
+  CheckCall( [ sys.executable, build_file ] + sys.argv[ 1: ] )
 
   # Remove old YCM libs if present so that YCM can start.
   old_libs = (