Comment 0 for bug 1834379

Using the following test file, and running python3 test.py, the program raises an error. However program exits with no output as expected on x86_64 and aarch64

```
# test.py
#!/usr/bin/env python3

import pygraphviz

graph = pygraphviz.AGraph()
graph.add_node('foo')
graph.add_node('bar')
graph.add_edge('foo', 'bar')
```

Error seen

```
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/pygraphviz/agraph.py", line 1561, in __new__
    nh = gv.agnode(graph.handle, n.encode(graph.encoding), _Action.find)
KeyError: 'agnode: no key'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "test.py", line 8, in <module>
    graph.add_edge('foo', 'bar')
  File "/usr/lib/python3/dist-packages/pygraphviz/agraph.py", line 478, in add_edge
    e = Edge(self, eh=eh)
  File "/usr/lib/python3/dist-packages/pygraphviz/agraph.py", line 1625, in __new__
    s = Node(graph, nh=source)
  File "/usr/lib/python3/dist-packages/pygraphviz/agraph.py", line 1563, in __new__
    raise KeyError("Node %s not in graph." % n)
KeyError: 'Node None not in graph.'
```

If I upgrade to 1.5 via pip after installing the apt dependency libgraphviz-dev, this same snippet works on all of these platforms.

It also works if I install pygraphviz 1.4rc1 from pip. Also, it seems to work with the debian package python3-pygraphviz 1.4 from cosmic. As far as I can tell, there are no differences between the cosmic and the bionic packages, other than it was rebuilt for Python 3.7.

Here's a summary:

OS pygraphviz version Installed from debian or pip Example Works?
Bionic 1.4~rc1 Debian No
Cosmic 1.4~rc1 Debian Yes
Disco 1.5 Debian Yes
Bionic 1.4~rc1 pip Yes
Bionic 1.5 pip Yes

And one more data point; if I pull down the debian sources (apt-get source python3-pygraphviz ; apt-get build-dep python3-pygraphviz), build with no modifications (debuild -uc -us), and then install (dpkg -i python3-pygraphviz_1.4~rc1-1build2_armhf.deb), it works just fine.

From all of this, I can only conclude that the Ubuntu Bionic armhf debian package is somehow corrupt. Perhaps a rebuild of the package would solve the problem.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: python3-pygraphviz 1.4~rc1-1build2
ProcVersionSignature: Ubuntu 4.15.0-1041.43-aws 4.15.18
Uname: Linux 4.15.0-1041-aws aarch64
ApportVersion: 2.20.9-0ubuntu7.6
Architecture: armhf
Date: Wed Jun 26 22:23:47 2019
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_US.UTF-8
SourcePackage: python-pygraphviz
UpgradeStatus: No upgrade log present (probably fresh install)