Graphviz version

[angelo-dalli]

The requirements.txt file seems to have a minor bug for the graphviz version, getting the following error from pip:

ERROR: Could not find a version that satisfies the requirement graphviz~=2.50.0 (from versions: 0.1, 0.1.1, 0.2, 0.2.1, 0.2.2, 0.3, 0.3.1, 0.3.2, 0.3.3, 0.3.4, 0.3.5, 0.4, 0.4.1, 0.4.2, 0.4.3, 0.4.4, 0.4.5, 0.4.6, 0.4.7, 0.4.8, 0.4.9, 0.4.10, 0.5, 0.5.1, 0.5.2, 0.6, 0.7, 0.7.1, 0.8, 0.8.1, 0.8.2, 0.8.3, 0.8.4, 0.9, 0.10, 0.10.1, 0.11, 0.11.1, 0.12, 0.13, 0.13.1, 0.13.2, 0.14, 0.14.1, 0.14.2, 0.15, 0.16, 0.17, 0.18, 0.18.1, 0.18.2, 0.19, 0.19.1, 0.19.2, 0.20, 0.20.1)
ERROR: No matching distribution found for graphviz~=2.50.0

I just installed graphviz manually but you may want to fix this

[rrtucci]

Okay, thanks. Will fix it by removing version number.