slapgrid: replace platform.linux_distribution() with distro.linux_distribution()

platform.linux_distribution() is deprecated since Python3.5 and it's
removed altogether in Python 3.8.

This more or less reverts 75b2d79c.

We don't need anymore the patch for Ubuntu as it is correctly supported
in distro module.

setup.py

@@ -77,6 +77,7 @@ setup(name=name,
           'jsonschema',
           'PyYAML',
           'uritemplate', # used by hateoas navigator
+          'distro',
           'subprocess32; python_version<"3"',
           'enum34; python_version<"3"',
           'ipaddress; python_version<"3"',  # used by whitelistfirewall

slapos/grid/distribution.py

@@ -33,20 +33,11 @@ Provides helper functions to check if two binary caches are compatible.
 os_matches(...):
     returns True if the arguments reference compatible platforms.
 
-patched_linux_distribution(...):
-    a patched version of platform.linux_distribution()
-
-    this is the same function provided with the python package in Debian and Ubuntu:
-        see http://bugs.python.org/issue9514
-
-    otherwise, Ubuntu will always be reported as an unstable Debian, regardless of the version.
-
 distribution_tuple()
-    returns a (distname, version, id) tuple under linux or cygwin
+    returns a (distname, version, id) tuple under linux
 """
 
-import platform
-import re
+import distro
 
 
 def _debianize(os_):
@@ -65,38 +56,5 @@ def os_matches(os1, os2):
     return _debianize(os1) == _debianize(os2)
 
 
-_distributor_id_file_re = re.compile(r"(?:DISTRIB_ID\s*=)\s*(.*)", re.I)
-_release_file_re = re.compile(r"(?:DISTRIB_RELEASE\s*=)\s*(.*)", re.I)
-_codename_file_re = re.compile(r"(?:DISTRIB_CODENAME\s*=)\s*(.*)", re.I)
-
-
-def patched_linux_distribution(distname='', version='', id='',
-                               supported_dists=platform._supported_dists,
-                               full_distribution_name=1):
-    # check for the Debian/Ubuntu /etc/lsb-release file first, needed so
-    # that the distribution doesn't get identified as Debian.
-    try:
-        etclsbrel = open("/etc/lsb-release", "rU")
-        for line in etclsbrel:
-            m = _distributor_id_file_re.search(line)
-            if m:
-                _u_distname = m.group(1).strip()
-            m = _release_file_re.search(line)
-            if m:
-                _u_version = m.group(1).strip()
-            m = _codename_file_re.search(line)
-            if m:
-                _u_id = m.group(1).strip()
-        if _u_distname and _u_version:
-            return (_u_distname, _u_version, _u_id)
-    except (EnvironmentError, UnboundLocalError):
-        pass
-
-    return platform.linux_distribution(distname, version, id, supported_dists, full_distribution_name)
-
-
 def distribution_tuple():
-    if platform.system().startswith('CYGWIN_'):
-        return (platform.system(), platform.platform(), '')
-    else:
-        return patched_linux_distribution()
+    return distro.linux_distribution(full_distribution_name=False)

slapos/grid/networkcache.py

@@ -15,7 +15,6 @@ from __future__ import print_function
 
 import ast
 import json
-import platform
 import shutil
 import subprocess
 import traceback