Moved 'Dropping' print from stdout to stderr in drop_versions.py (#6071)

Printing 'Dropping' debug strings to stdout leads to write in package json.
This moved that to stderr stream.

Author: Subhajitdas298

package/drop_versions.py

@@ -19,7 +19,9 @@ def drop_version(todrop, obj):
     out = [];
     for o in obj:
         version = o['version'].encode('ascii')
-        if version != todrop:
+        if version == todrop:
+            print("Dropping version {0}".format(todrop), file=sys.stderr)
+        else:
             out.append(o)
     return out