diff --git a/src/yunohost/data_migrations/0003_migrate_to_stretch.py b/src/yunohost/data_migrations/0003_migrate_to_stretch.py
index a15d786df..41ab6b4b2 100644
--- a/src/yunohost/data_migrations/0003_migrate_to_stretch.py
+++ b/src/yunohost/data_migrations/0003_migrate_to_stretch.py
@@ -1,10 +1,5 @@
 import glob
 import os
-import requests
-import base64
-import time
-import json
-import errno
 from shutil import copy2
 
 from moulinette import m18n, msettings
@@ -16,7 +11,6 @@ from moulinette.utils.filesystem import read_file
 from yunohost.tools import Migration
 from yunohost.app import unstable_apps
 from yunohost.service import (_run_service_command,
-                              service_regen_conf,
                               manually_modified_files,
                               manually_modified_files_compared_to_debian_default)
 from yunohost.utils.filesystem import free_space_in_directory
@@ -24,7 +18,8 @@ from yunohost.utils.packages import get_installed_version
 
 logger = getActionLogger('yunohost.migration')
 
-YUNOHOST_PACKAGES = ["yunohost", "yunohost-admin", "moulinette", "ssowat" ]
+YUNOHOST_PACKAGES = ["yunohost", "yunohost-admin", "moulinette", "ssowat"]
+
 
 class MyMigration(Migration):
     "Upgrade the system to Debian Stretch and Yunohost 3.0"
@@ -103,7 +98,7 @@ class MyMigration(Migration):
         # in the middle and debian version could be >= 9.x but yunohost package
         # would still be in 2.x...
         if not self.debian_major_version() == 8 \
-        and not self.yunohost_major_version() == 2:
+           and not self.yunohost_major_version() == 2:
             raise MoulinetteError(m18n.n("migration_0003_not_jessie"))
 
         # Have > 1 Go free space on /var/ ?
@@ -113,7 +108,7 @@ class MyMigration(Migration):
         # Check system is up to date
         # (but we don't if 'stretch' is already in the sources.list ...
         # which means maybe a previous upgrade crashed and we're re-running it)
-        if not " stretch " in read_file("/etc/apt/sources.list"):
+        if " stretch " not in read_file("/etc/apt/sources.list"):
             self.apt_update()
             apt_list_upgradable = check_output("apt list --upgradable -a")
             if "upgradable" in apt_list_upgradable:
@@ -128,12 +123,12 @@ class MyMigration(Migration):
         # in the middle and debian version could be >= 9.x but yunohost package
         # would still be in 2.x...
         if not self.debian_major_version() == 8 \
-        and not self.yunohost_major_version() == 2:
+           and not self.yunohost_major_version() == 2:
             return None
 
         # Get list of problematic apps ? I.e. not official or community+working
         problematic_apps = unstable_apps()
-        problematic_apps = "".join(["\n    - "+app for app in problematic_apps ])
+        problematic_apps = "".join(["\n    - " + app for app in problematic_apps])
 
         # Manually modified files ? (c.f. yunohost service regen-conf)
         modified_files = manually_modified_files()
@@ -141,7 +136,7 @@ class MyMigration(Migration):
         # modified and needs to be upgraded...
         if "/etc/nginx/nginx.conf" in manually_modified_files_compared_to_debian_default():
             modified_files.append("/etc/nginx/nginx.conf")
-        modified_files = "".join(["\n    - "+f for f in modified_files ])
+        modified_files = "".join(["\n    - " + f for f in modified_files])
 
         message = m18n.n("migration_0003_general_warning")
 
@@ -232,7 +227,6 @@ class MyMigration(Migration):
 
         os.system(command)
 
-
     def apt_dist_upgrade(self, conf_flags):
 
         # Make apt-get happy
@@ -264,7 +258,6 @@ class MyMigration(Migration):
             # enabled if the user explicitly add --verbose ...
             os.system(command)
 
-
     # Those are files that should be kept and restored before the final switch
     # to yunohost 3.x... They end up being modified by the various dist-upgrades
     # (or need to be taken out momentarily), which then blocks the regen-conf
@@ -304,4 +297,3 @@ class MyMigration(Migration):
         for f in self.files_to_keep:
             dest_file = f.strip('/').replace("/", "_")
             copy2(os.path.join(tmp_dir, dest_file), f)
-