to perform usability tests. This will avoid raising IndexError
when choosing an exit.

GH: closes #218

Since version 3.4.2 gives error on install_layout and it is not
the default in stable OS distributions

**Important changes**:

- Result format changed, causing a version bump to 4. Updating sbws to 0.5.0
  will cause it to ignore results with version less than 4.

Summary of changes:

- Keep previously-generated v3bw files
- Allow a relay to limit its weight based on
  RelayBandwidthRate/MaxAdvertisedBandwidth
- 1 CPU usage optimization
- 1 memory usage optimization

Check that there are results before trying to get the results
for an specific relay. This would avoid raising TypeError
when there are not results.

log the error, ingore the line and continue

Matt Traudt authored Jun 22, 2018 and juga committed Jun 24, 2018

The chance of us needing a refresh at this point is TINY, but it's probably
better to return a list of relays stale by a millisecond than it is to cause
the user's program to crash.

Matt Traudt authored Jun 22, 2018 and juga committed Jun 24, 2018

I'm not sure if this is necessary, honestly. But it doesn't hurt.

Matt Traudt authored Jun 22, 2018 and juga committed Jun 24, 2018

GH: ref #205

Matt Traudt authored Jun 22, 2018 and juga committed Jun 24, 2018

This reduces the number of copies of relay descriptors we have to keep
in memory and how frequently we stop to refresh those descriptors.

Implement the "MaxAdvertisedBandwidth" hack ...

GH: closes #204

This required a bump in the result version: we add a new field to
ResultSuccess.