diff --git a/bin/yunohost-api b/bin/yunohost-api
index 470f61c6..3e8e7e31 100755
--- a/bin/yunohost-api
+++ b/bin/yunohost-api
@@ -196,12 +196,12 @@ if __name__ == '__main__':
 
     # Run the server
     from moulinette import api, MoulinetteError
-    from yunohost import get_versions
+    from yunohost.utils.packages import ynh_packages_version
     ret = api(_retrieve_namespaces(),
             host=opts.host, port=opts.port,
             routes={
                 ('GET', '/installed'): is_installed,
-                ('GET', '/version'): get_versions,
+                ('GET', '/version'): ynh_packages_version,
             },
             use_cache=opts.use_cache, use_websocket=opts.use_websocket
     )
diff --git a/data/actionsmap/yunohost.yml b/data/actionsmap/yunohost.yml
index 4e09d68d..721d3334 100644
--- a/data/actionsmap/yunohost.yml
+++ b/data/actionsmap/yunohost.yml
@@ -57,7 +57,7 @@ _global:
             help: Display YunoHost packages versions
             action: callback
             callback:
-                method: yunohost.get_versions
+                method: yunohost.utils.packages.ynh_packages_version
                 return: true
 
 #############################
diff --git a/locales/en.json b/locales/en.json
index e6bef7ab..6852e9c6 100644
--- a/locales/en.json
+++ b/locales/en.json
@@ -202,6 +202,10 @@
     "user_info_failed" : "Unable to retrieve user information",
     "user_home_creation_failed" : "Unable to create user home folder",
 
+    "package_unexpected_error" : "An unexpected error occured with the package '{pkgname}'",
+    "package_unknown" : "Unknown package '{pkgname}'",
+    "package_not_installed" : "Package '{pkgname}' is not installed",
+
     "admin_password" : "Administration password",
     "ask_firstname" : "First name",
     "ask_lastname" : "Last name",
diff --git a/src/yunohost/__init__.py b/src/yunohost/__init__.py
index 5bfacdca..e69de29b 100644
--- a/src/yunohost/__init__.py
+++ b/src/yunohost/__init__.py
@@ -1,50 +0,0 @@
-# -*- coding: utf-8 -*-
-
-""" YunoHost scripts for the moulinette """
-
-""" License
-
-    Copyright (C) 2015 YUNOHOST.ORG
-
-    This program is free software; you can redistribute it and/or modify
-    it under the terms of the GNU Affero General Public License as published
-    by the Free Software Foundation, either version 3 of the License, or
-    (at your option) any later version.
-
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU Affero General Public License for more details.
-
-    You should have received a copy of the GNU Affero General Public License
-    along with this program; if not, see http://www.gnu.org/licenses
-
-"""
-
-## Packages versions
-
-def get_version(package):
-    """Get the version of package"""
-    from moulinette.utils import process
-    return process.check_output(
-        "dpkg-query -W -f='${{Version}}' {0}".format(package)
-    ).strip()
-
-def get_versions(*args, **kwargs):
-    """Get the version of each YunoHost package"""
-    from collections import OrderedDict
-    return OrderedDict([
-        ('moulinette', get_version('moulinette')),
-        ('yunohost', get_version('yunohost')),
-        ('yunohost-admin', get_version('yunohost-admin')),
-        ('ssowat', get_version('ssowat')),
-    ])
-
-def has_min_version(min_version, package='yunohost', strict=False):
-    """Check if a package has minimum version"""
-    from distutils.version import LooseVersion, StrictVersion
-    cmp_cls = StrictVersion if strict else LooseVersion
-    version = cmp_cls(get_version(package))
-    if version >= cmp_cls(min_version):
-        return True
-    return False
diff --git a/src/yunohost/app.py b/src/yunohost/app.py
index a9cfeb66..4ee7883a 100644
--- a/src/yunohost/app.py
+++ b/src/yunohost/app.py
@@ -39,8 +39,8 @@ import subprocess
 from moulinette.core import MoulinetteError
 from moulinette.utils.log import getActionLogger
 
-from . import has_min_version
-from .service import service_log
+from yunohost.service import service_log
+from yunohost.utils.packages import has_min_version
 
 logger = getActionLogger('yunohost.app')
 
diff --git a/src/yunohost/utils/__init__.py b/src/yunohost/utils/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/src/yunohost/utils/packages.py b/src/yunohost/utils/packages.py
new file mode 100644
index 00000000..c4f4fe76
--- /dev/null
+++ b/src/yunohost/utils/packages.py
@@ -0,0 +1,100 @@
+# -*- coding: utf-8 -*-
+
+""" License
+
+    Copyright (C) 2015 YUNOHOST.ORG
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as published
+    by the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Affero General Public License for more details.
+
+    You should have received a copy of the GNU Affero General Public License
+    along with this program; if not, see http://www.gnu.org/licenses
+
+"""
+from collections import OrderedDict
+
+import apt
+from apt_pkg import version_compare
+
+
+# Exceptions -----------------------------------------------------------------
+
+class PackageException(Exception):
+    """Base exception related to a package
+
+    Represent an exception related to the package named `pkgname`. If no
+    `message` is provided, it will first try to use the translation key
+    `message_key` if defined by the derived class. Otherwise, a standard
+    message will be used.
+
+    """
+    message_key = 'package_unexpected_error'
+
+    def __init__(self, pkgname, message=None):
+        super(PackageException, self).__init__(
+            message or m18n.n(self.message_key, pkgname=pkgname))
+        self.pkgname = pkgname
+
+
+class UnknownPackage(PackageException):
+    message_key = 'package_unknown'
+
+
+class UninstalledPackage(PackageException):
+    message_key = 'package_not_installed'
+
+
+# Packages and cache helpers -------------------------------------------------
+
+def get_installed_version(*pkgnames, **kwargs):
+    """Get the installed version of package(s)
+
+    Retrieve one or more packages named `pkgnames` and return their installed
+    version as a dict or as a string if only one is requested. If `strict` is
+    `True`, an exception will be raised if a package is unknown or not
+    installed.
+
+    """
+    cache = apt.Cache()
+    strict = kwargs.get('strict', False)
+    versions = OrderedDict()
+    for pkgname in pkgnames:
+        try:
+            pkg = cache[pkgname]
+        except KeyError:
+            if strict:
+                raise UnknownPackage(pkgname)
+            logger.warning(m18n.n('package_unknown', pkgname=pkgname))
+        try:
+            version = pkg.installed.version
+        except AttributeError:
+            if strict:
+                raise UninstalledPackage(pkgname)
+            version = None
+        versions[pkgname] = version
+    if len(pkgnames) == 1:
+        return versions[pkgnames[0]]
+    return versions
+
+def has_min_version(min_version, package='yunohost'):
+    """Check if a package has a minimum installed version"""
+    version = get_installed_version(package)
+    if version_compare(version, min_version) > 0:
+        return True
+    return False
+
+
+# YunoHost related methods ---------------------------------------------------
+
+def ynh_packages_version(*args, **kwargs):
+    """Return the version of each YunoHost package"""
+    return get_installed_version(
+        'yunohost', 'yunohost-admin', 'moulinette', 'ssowat',
+    )