[Bug 1834379] [NEW] armhf Bionic python3-pygraphviz package errors for simple use case

[Emerson Knapp]

Public bug reported:

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:

Bionic	1.4~rc1	Debian	Broken
Cosmic	1.4~rc1	Debian	Works
Disco	1.5	Debian	Works
Bionic	1.4~rc1	pip	Works
Bionic	1.5	pip	Works

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)

** Affects: python-pygraphviz (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: apport-bug armhf bionic

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https://bugs.launchpad.net/bugs/1834379

Title:
  armhf Bionic python3-pygraphviz package errors for simple use case

Status in python-pygraphviz package in Ubuntu:
  New

Bug description:
  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:

  Bionic	1.4~rc1	Debian	Broken
  Cosmic	1.4~rc1	Debian	Works
  Disco	1.5	Debian	Works
  Bionic	1.4~rc1	pip	Works
  Bionic	1.5	pip	Works

  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)

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