Adjust requirements and lower-constraints

Conservative changes to get the l-c job passing with the new
pip resolver.

Big changes:
- pytz 2013.6 -> 2015.7 (u-c allows 2020.1)
  * needed for babel
- tempest 17.1.0 -> 24.0.0 (u-c allows 25.0.1)
  * for dulwich (long story)
- urllib3 1.21.1 -> 1.24.1 (u-c allows 1.25.10)
  * for tempest
- oslo.concurrency 3.25.0 -> 3.26.0 (u-c allows 4.3.1)
  * for tempest
- mccabe 0.2.1 -> 0.6.0
  * for flake8

Also added dulwich to test-requirements to narrow down versions
considered by the resolver.

Change-Id: I8bb622c947cada2905e8d756d5a64f08abaeee8d

lower-constraints.txt

@@ -7,6 +7,7 @@ cryptography==2.7
 ddt==1.0.1
 debtcollector==1.2.0
 doc8==0.6.0
+dulwich==0.20.6
 extras==1.0.0
 fasteners==0.7.0
 fixtures==3.0.0
@@ -16,12 +17,12 @@ iso8601==0.1.11
 jsonschema==2.6.0
 keystoneauth1==3.4.0
 linecache2==1.0.0
-mccabe==0.2.1
+mccabe==0.6.0
 monotonic==0.6
 msgpack-python==0.4.0
 netaddr==0.7.18
 netifaces==0.10.4
-oslo.concurrency==3.25.0
+oslo.concurrency==3.26.0
 oslo.config==5.2.0
 oslo.context==2.19.2
 oslo.i18n==3.15.3
@@ -39,7 +40,7 @@ pyperclip==1.5.27
 python-dateutil==2.5.3
 python-mimeparse==1.6.0
 python-subunit==1.0.0
-pytz==2013.6
+pytz==2015.7
 PyYAML==3.13
 reno==3.1.0
 requests-mock==1.2.0
@@ -49,10 +50,10 @@ simplejson==3.5.1
 six==1.10.0
 stestr==1.0.0
 stevedore==1.20.0
-tempest==17.1.0
+tempest==24.0.0
 testrepository==0.0.18
 testtools==2.2.0
 traceback2==1.4.0
 unittest2==1.1.0
-urllib3==1.21.1
+urllib3==1.24.1
 wrapt==1.7.0

test-requirements.txt

@@ -9,8 +9,12 @@ ddt>=1.0.1 # MIT
 fixtures>=3.0.0 # Apache-2.0/BSD
 reno>=3.1.0 # Apache-2.0
 requests-mock>=1.2.0 # Apache-2.0
-tempest>=17.1.0 # Apache-2.0
+tempest>=24.0.0 # Apache-2.0
 testtools>=2.2.0 # MIT
 stestr>=1.0.0 # Apache-2.0
 oslo.serialization!=2.19.1,>=2.18.0 # Apache-2.0
 doc8>=0.6.0 # Apache-2.0
+#
+# these indirect dependencies are added to narrow down the range
+# considered by the pip resolver
+dulwich>=0.20.6