Merge ~cjwatson/launchpad:string-ascii into launchpad:master

[Colin Watson]

Use string.ascii_{letters,lowercase}

Python 3 removed string.letters and string.lowercase.

[Ioana Lasc (ilasc)]

review: Approve

diff --git a/lib/lp/bugs/adapters/treelookup.py b/lib/lp/bugs/adapters/treelookup.py
index 45acab5..3c35c22 100644
--- a/lib/lp/bugs/adapters/treelookup.py
+++ b/lib/lp/bugs/adapters/treelookup.py
@@ -110,7 +110,7 @@ class LookupBranch:
         else:
             return format % self.result.describe(level)
 
-    _describe_key_chars = set(string.letters + string.digits + '-_+=*')
+    _describe_key_chars = set(string.ascii_letters + string.digits + '-_+=*')
 
     def _describe_key(self, key):
         """Return a pretty representation of a simple key.
diff --git a/lib/lp/services/testing/tests/test_customresult.py b/lib/lp/services/testing/tests/test_customresult.py
index 338ca2e..0baf596 100644
--- a/lib/lp/services/testing/tests/test_customresult.py
+++ b/lib/lp/services/testing/tests/test_customresult.py
@@ -41,7 +41,7 @@ class TestFilterTests(TestCase):
         f.flush()
 
     @staticmethod
-    def make_suite(testnames=string.lowercase):
+    def make_suite(testnames=string.ascii_lowercase):
         """Make a suite containing `testnames` (default: 'a'..'z')."""
         suite = unittest.TestSuite()
         for testname in testnames:
@@ -55,8 +55,8 @@ class TestFilterTests(TestCase):
         The first has 'a'..'m' and the second 'n'..'z'.
         """
         return (
-            TestFilterTests.make_suite(string.lowercase[:13]),
-            TestFilterTests.make_suite(string.lowercase[13:]),
+            TestFilterTests.make_suite(string.ascii_lowercase[:13]),
+            TestFilterTests.make_suite(string.ascii_lowercase[13:]),
             )
 
     @staticmethod
diff --git a/lib/lp/snappy/model/snapstoreclient.py b/lib/lp/snappy/model/snapstoreclient.py
index 7d094aa..9d007de 100644
--- a/lib/lp/snappy/model/snapstoreclient.py
+++ b/lib/lp/snappy/model/snapstoreclient.py
@@ -83,7 +83,7 @@ class MacaroonAuth(requests.auth.AuthBase):
     """Attaches macaroon authentication to a given Request object."""
 
     # The union of the base64 and URL-safe base64 alphabets.
-    allowed_chars = set(string.digits + string.letters + "+/=-_")
+    allowed_chars = set(string.digits + string.ascii_letters + "+/=-_")
 
     def __init__(self, root_macaroon_raw, unbound_discharge_macaroon_raw=None,
                  logger=log):