Check if file was changed before upload

Use sha1 hash of file, which is available via FileInfo() to check for
changes

euroexange/euroexange.py

@@ -25,6 +25,7 @@ import zipfile
 import shlex
 import subprocess
 import email.utils
+import hashlib
 
 import pywikibot
 
@@ -226,7 +227,11 @@ class EuroExangeBot( pywikibot.bot.BaseBot ):
         if self.image_update_needed():
             self.call_gnuplot( job )
 
-            self.upload_file( job )
+            if self.file_changed():
+                self.upload_file( job )
+            else:
+                jogobot.output( "No upload needed for Job {}.".format(
+                self.current_job.image) )
 
         # Nothing to do
         else:
@@ -274,6 +279,26 @@ class EuroExangeBot( pywikibot.bot.BaseBot ):
 
         subprocess.call( cmd, cwd=self.wdir, env=plt_env )
 
+    def file_changed( self ):
+        """
+        Checks if generated file and online file differs via sha1 hash
+
+        @returns True if file was changed
+        @rtype bool
+        """
+
+        # Get online file sha1 hash
+        online_sha1 = self.current_job.filepage.latest_file_info.sha1
+
+        # Get local file sha1 hash
+        with open(os.path.join(self.wdir, self.current_job.image),'rb') as fd:
+            local_sha1 = hashlib.sha1(fd.read()).hexdigest()
+
+        if online_sha1 == local_sha1:
+            return False
+        else:
+            return True
+
     def upload_file( self, job ):
         """