fix an UnboundLocalError when the release file is empty #7773

Lib/platform.py

@@ -263,6 +263,12 @@ _supported_dists = (
 
 def _parse_release_file(firstline):
 
+    # Default to empty 'version' and 'id' strings.  Both defaults are used
+    # when 'firstline' is empty.  'id' defaults to empty when an id can not
+    # be deduced.
+    version = ''
+    id = ''
+
     # Parse the first line
     m = _lsb_release_version.match(firstline)
     if m is not None:
@@ -280,8 +286,6 @@ def _parse_release_file(firstline):
         version = l[0]
         if len(l) > 1:
             id = l[1]
-        else:
-            id = ''
     return '', version, id
 
 def linux_distribution(distname='', version='', id='',

Lib/test/test_platform.py

@@ -198,6 +198,7 @@ class PlatformTest(unittest.TestCase):
             ('Red Hat Enterprise Linux release 4 (Nahant)', ('Red Hat Enterprise Linux', '4', 'Nahant')),
             ('CentOS release 4', ('CentOS', '4', None)),
             ('Rocks release 4.2.1 (Cydonia)', ('Rocks', '4.2.1', 'Cydonia')),
+            ('', ('', '', '')), # If there's nothing there.
             ):
             self.assertEqual(platform._parse_release_file(input), output)
 

Misc/ACKS

@@ -357,6 +357,7 @@ Jeremy Hylton
 Gerhard Häring
 Mihai Ibanescu
 Lars Immisch
+Meador Inge
 Tony Ingraldi
 John Interrante
 Bob Ippolito

Misc/NEWS

@@ -42,6 +42,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #7773: Fix an UnboundLocalError in platform.linux_distribution() when
+  the release file is empty.
+
 - Issue #7748: Since unicode values are supported for some metadata options
   in Distutils, the DistributionMetadata get_* methods will now return an utf-8
   encoded string for them. This ensure that the upload and register commands