Update pylint to 1.7.6, uncap networkx

This review squashes:
    Iac9afc7766d3640815dc20cfd6de1245d36a09cc
    Ie894b5801bd7b3815432882cd626941e89d9f9a1

We need to do this as we can't fix pylint without networkx as that
failes requirements-chak due to us having a cap on networkx and we can't
uncap networkx as part of tripleo-buildimage installs without
constratints which gets us 2.1 and DIB desn't support 2.x

This is the commit message Iac9afc7766d3640815dc20cfd6de1245d36a09cc
---
One of the pylint dependencies has updated to be python3 only; this
version of pylint correctly caps things so it still works with
python2.

This also exposes that we need to uncap networkx due to
I34045f87ca19c2f184b040f4d89347374cce518b.  We should remain on
version 1 for now thanks to upper-constraints, but we need to maintain
the lower-constraint.
---

This is the commit message Ie894b5801bd7b3815432882cd626941e89d9f9a1
---
Support different versions of networkx

Since the entry of networkx 2.0 nodes has a different
behaviour. Checking if dg.nodes is iterable is enough to add
compatibility for new/older versions.
---

Change-Id: I82dc61fac6c156a4f0d574290c7632077aa53195

diskimage_builder/block_device/config.py

@@ -159,6 +159,12 @@ def create_graph(config, default_config, state):
     # add the appropriate nodes and edges.
     dg = nx.DiGraph()
 
+    # check about dg.nodes, to support different networkx versions
+    if hasattr(dg.nodes, '__iter__'):
+        dg_nodes = dg.nodes
+    else:
+        dg_nodes = dg.node
+
     for config_entry in config:
         # this should have been checked by generate_config
         assert len(config_entry) == 1
@@ -190,7 +196,7 @@ def create_graph(config, default_config, state):
             # ensure node names are unique.  networkx by default
             # just appends the attribute to the node dict for
             # existing nodes, which is not what we want.
-            if node.name in dg.node:
+            if node.name in dg_nodes:
                 raise BlockDeviceSetupException(
                     "Duplicate node name: %s" % (node.name))
             logger.debug("Adding %s : %s", node.name, node)
@@ -210,12 +216,12 @@ def create_graph(config, default_config, state):
         logger.debug("Edges for %s: f:%s t:%s", name,
                      edges_from, edges_to)
         for edge_from in edges_from:
-            if edge_from not in dg.node:
+            if edge_from not in dg_nodes:
                 raise BlockDeviceSetupException(
                     "Edge not defined: %s->%s" % (edge_from, name))
             dg.add_edge(edge_from, name)
         for edge_to in edges_to:
-            if edge_to not in dg.node:
+            if edge_to not in dg_nodes:
                 raise BlockDeviceSetupException(
                     "Edge not defined: %s->%s" % (name, edge_to))
             dg.add_edge(name, edge_to)
@@ -231,9 +237,9 @@ def create_graph(config, default_config, state):
 
     # Topological sort (i.e. create a linear array that satisfies
     # dependencies) and return the object list
-    call_order_nodes = nx.topological_sort(dg)
-    logger.debug("Call order: %s", list(call_order_nodes))
-    call_order = [dg.node[n]['obj'] for n in call_order_nodes]
+    call_order_nodes = list(nx.topological_sort(dg))
+    logger.debug("Call order: %s", call_order_nodes)
+    call_order = [dg_nodes[n]['obj'] for n in call_order_nodes]
 
     return dg, call_order
 

requirements.txt

@@ -2,7 +2,7 @@
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
 Babel!=2.4.0,>=2.3.4 # BSD
-networkx<2.0,>=1.10 # BSD
+networkx>=1.10 # BSD
 pbr!=2.1.0,>=2.0.0 # Apache-2.0
 PyYAML>=3.12 # MIT
 flake8<2.6.0,>=2.5.4 # MIT

test-requirements.txt

@@ -2,7 +2,7 @@
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
 hacking<0.11,>=0.10.0
-pylint==1.7.1 # GPLv2
+pylint==1.7.6 # GPLv2
 
 fixtures>=3.0.0 # Apache-2.0/BSD
 mock>=2.0.0 # BSD