Set correct mtime of zip file

Since we are writing the zip file with python, the original mdate, on
which is_zip_uptodate() relies gets lost. Therefore overwrite it with
value of "Last-Modified" HTTP header

euroexange/euroexange.py

@@ -24,6 +24,7 @@ import datetime
 import zipfile
 import shlex
 import subprocess
+import email.utils
 
 import pywikibot
 
@@ -167,6 +168,15 @@ class EuroExangeBot( pywikibot.bot.BaseBot ):
 
             shutil.copyfileobj(response, out_file)
 
+            # Extract original change date from http header
+            # We need to set it later, since we write a new file
+            mdate = email.utils.parsedate_to_datetime(
+                response.info()["Last-Modified"])
+
+        # Set ctime to value from http header
+        os.utime( os.path.join(self.wdir, type(self).zip_file),
+                     (datetime.datetime.now().timestamp(), mdate.timestamp()) )
+
     def extract_csv( self ):
         """
         Extract csv file from zip archive