Check for --rj-include-dir earlier

This targets issue #110, and fixups commit c4df408: I'm quite surprised that this went unnoticed when I closed issue #60... sorry.

Author: lelit

setup.py

@@ -3,7 +3,7 @@
 # :Author: Ken Robbins <ken@kenrobbins.com>
 # :License: MIT License
 # :Copyright: © 2015 Ken Robbins
-# :Copyright: © 2016, 2017 Lele Gaifax
+# :Copyright: © 2016, 2017, 2018 Lele Gaifax
 #
 
 import os.path
@@ -29,11 +29,19 @@
 
 ROOT_PATH = os.path.abspath(os.path.dirname(__file__))
 
-if not os.path.isdir(os.path.join(ROOT_PATH, 'rapidjson', 'include')):
- raise RuntimeError("RapidJSON sources not found: if you cloned the git repository,"
- " you should initialize the rapidjson submodule as explained in"
- " the README.rst; in all other cases you may want to report the"
- " issue.")
+rj_include_dir = './rapidjson/include'
+
+for idx, arg in enumerate(sys.argv[:]):
+ if arg.startswith('--rj-include-dir='):
+ sys.argv.pop(idx)
+ rj_include_dir = arg.split('=', 1)[1]
+ break
+else:
+ if not os.path.isdir(os.path.join(ROOT_PATH, 'rapidjson', 'include')):
+ raise RuntimeError("RapidJSON sources not found: if you cloned the git"
+ " repository, you should initialize the rapidjson submodule"
+ " as explained in the README.rst; in all other cases you may"
+ " want to report the issue.")
 
 with open('version.txt', encoding='utf-8') as f:
  VERSION = f.read()
@@ -44,14 +52,6 @@
 with open('CHANGES.rst', encoding='utf-8') as f:
  CHANGES = f.read()
 
-rj_include_dir = './rapidjson/include'
-
-for idx, arg in enumerate(sys.argv[:]):
- if arg.startswith('--rj-include-dir='):
- sys.argv.pop(idx)
- rj_include_dir = arg.split('=', 1)[1]
- break
-
 extension_options = {
  'sources': ['./rapidjson.cpp'],
  'include_dirs': [rj_include_dir],