API CHANGE: replace print_version_and_exit with format_version

The --version option was previously subject to syntax validation of
other args when it shouldn't be.  This commit switches to a 'version'
arg type, but this comes at the cost of replacing the
print_version_and_exit function with a format_version function that
simply returns the version string.

requestbuilder/command.py

@@ -161,8 +161,8 @@ class BaseCommand(object):
         parser.add_argument('--debugger', action='store_true', dest='_debugger',
                             default=argparse.SUPPRESS,
                             help='launch interactive debugger on error')
-        parser.add_argument('--version', action='store_true', dest='_version',
-                            default=argparse.SUPPRESS,
+        parser.add_argument('--version', action='version',
+                            version=self.suite.format_version(),
                             help="show the program's version and exit")
         if any('-h' in arg_obj.pargs for arg_obj in arg_objs
                if isinstance(arg_obj, Arg)):
@@ -224,8 +224,6 @@ class BaseCommand(object):
         if cli_args.pop('_debugger', False):
             self.__debug = True
             sys.excepthook = _debugger_except_hook
-        if cli_args.get('_version', False):
-            self.suite.print_version_and_exit()
         # Everything goes in self.args.  distribute_args() also puts them
         # elsewhere later on in the process.
         self.args.update(cli_args)

requestbuilder/suite.py

@@ -13,9 +13,9 @@
 # OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 
 import platform
+from requestbuilder import __version__
 import requests
 import sys
-from . import __version__
 
 
 class RequestBuilder(object):
@@ -27,9 +27,8 @@ class RequestBuilder(object):
         self.__user_agent = None
 
     @staticmethod
-    def print_version_and_exit():
-        print >> sys.stderr, 'requestbuilder', __version__, '(Prelude)'
-        sys.exit()
+    def format_version():
+        return 'requestbuilder {0} (Prelude)'.format(__version__)
 
     @staticmethod
     def list_config_files():