Fix lower-constraints

Change-Id: Id0c035fd8e83ad088520b264e2727fc1a42dd3e2

lower-constraints.txt

@@ -6,9 +6,9 @@ oslo.serialization==2.28.1
 oslo.utils==3.33.0
 oslotest==3.2.0
 pbr==2.0.0
-pylint==1.9.2
+pylint==2.5.3
 python-subunit==1.0.0
-six==1.10.0
+six==1.12
 sphinxcontrib-svg2pdfconverter==0.1.0
 stestr==2.0.0
 tenacity==5.0.2

test-requirements.txt

@@ -7,7 +7,7 @@ hacking>=3.0.1,<3.1.0 # Apache-2.0
 bandit!=1.6.0,>=1.1.0 # Apache-2.0
 coverage>=4.0,!=4.4 # Apache-2.0
 doc8>=0.6.0 # Apache-2.0
-pylint>=2.2.0 # GPLv2
+pylint>=2.5.3 # GPLv2
 python-subunit>=1.0.0 # Apache-2.0/BSD
 oslo.utils>=3.33.0 # Apache-2.0
 oslotest>=3.2.0 # Apache-2.0