[entropy.server] improve reliability of Server._setup_repository_package_filename

Providing the EntropyRepository instance currently in use is much
better than opening a new one.

libraries/entropy/server/interfaces/main.py

@@ -4216,8 +4216,8 @@ class ServerRepositoryMixin:
                     header = darkred("    # ")
                 )
 
-        download_url = self._setup_repository_package_filename(idpackage,
-            repo = repo)
+        download_url = self._setup_repository_package_filename(dbconn,
+            idpackage)
         destination_path = self.complete_local_upload_package_path(
             download_url, repo = repo)
         destination_dir = os.path.dirname(destination_path)
@@ -4232,18 +4232,16 @@ class ServerRepositoryMixin:
         return idpackage, destination_path
 
     # this function changes the final repository package filename
-    def _setup_repository_package_filename(self, idpackage, repo = None):
-
-        dbconn = self.open_server_repository(read_only = False,
-            no_upload = True, repo = repo)
+    def _setup_repository_package_filename(self, dbconn, idpackage):
 
         downloadurl = dbconn.retrieveDownloadURL(idpackage)
         packagerev = dbconn.retrieveRevision(idpackage)
         downloaddir = os.path.dirname(downloadurl)
         downloadfile = os.path.basename(downloadurl)
         # add revision
-        downloadfile = downloadfile[:-5]+"~%s%s" % (packagerev,
-            etpConst['packagesext'],)
+        pkg_ext = etpConst['packagesext']
+        downloadfile = downloadfile[:-len(pkg_ext)]+"~%s%s" % (packagerev,
+            pkg_ext,)
         downloadurl = os.path.join(downloaddir, downloadfile)
 
         # update url