Test if using python3 at the beginning of the script, and change shebang to do not force python3, as it enforce default python3 value and thus the check failed even if python2 is used

prismedia_upload.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python3
+#!/usr/bin/env python
 # coding: utf-8
 
 """
@@ -63,8 +63,11 @@ Languages:
     Japanese, Korean, Mandarin, Portuguese, Punjabi, Russian, Spanish
 
 """
-from os.path import dirname, realpath
 import sys
+if sys.version_info[0] < 3:
+    raise Exception("Python 3 or a more recent version is required.")
+
+from os.path import dirname, realpath
 import datetime
 import locale
 import logging
@@ -96,9 +99,6 @@ except ImportError:
                   'see https://github.com/ahupp/python-magic\n')
     exit(1)
 
-if sys.version_info[0] < 3:
-    raise Exception("Python 3 or a more recent version is required.")
-
 VERSION = "prismedia v0.7.1"
 
 VALID_PRIVACY_STATUSES = ('public', 'private', 'unlisted')