...so rdsys is able to read them too.

Reload BridgeDB by sending it a SIGHUP signal.

Closes bridgedb#40001

See merge request tpo/anti-censorship/bridgedb-admin!1

...because the --reload switch doesn't work.  It's supported but
doesn't actually reload BridgeDB.  Instead, when running bridgedb
--reload, one starts a second process, which then dies because it cannot
bind to the necessary ports (because the original BridgeDB instance is
already bound).

This partially fixes tpo/anti-censorship/bridgedb#40001.

We already have our git history, so there's no reason to maintain a
messy changelog on top of that.

This fixes <https://bugs.torproject.org/17548>.

We will be sending regular bridge requests from
testbridgestorbrowser@gmail.com.  We therefore want this address to be
whitelisted.

This is part of fixing <https://bugs.torproject.org/12802>.

...and clean up unused variables.

If flog doesn't exist, `which flog` will return the string "flog not
found" instead of an empty string.  Bash's built-in command "hash" is a
better way to do this.

FTE is no longer part of Tor Browser, and obfs3 and scramblesuit don't
offer anything that obfs4 doesn't already provide.

This fixes <https://bugs.torproject.org/33299>.

This patch fixes <https://bugs.torproject.org/32105>.

This fixes <https://bugs.torproject.org/19332> on the anti-censorship
team's side.

That's a better plan than just having the file grow endlessly because
BridgeDB appends new metrics to bridgedb-metrics.log.  We are going to
archive BridgeDB's metrics in CollecTor, so we won't lose any data
because of the log rotation.

This was discussed in <https://bugs.torproject.org/29480>.

Karsten asked for a new path on colchicifolium, which is why we're
updating our environment variables:
<https://bugs.torproject.org/29480#comment:8>

We added these options in the following ticket, which implemented an
anti-bot mechanism: <https://bugs.torproject.org/31252>.  In
BLACKLISTED_REQUEST_HEADERS_FILE, we will configure regular expressions
that help us identify bots.  Bot requests may then be served decoy
bridges, which are configured in DECOY_BRIDGES_FILE.

We added this feature in the following ticket:
<https://bugs.torproject.org/9316>

In addition to configuring a log file, we also need to change the
structure of the TASKS dictionary because we changed it as part of our
work for #9316.

Finally, we currently don't need PROXY_LIST_FILES -- all Tor exit relays
are fetched automatically and periodically updated.

We cannot establish a TCP connection to any of these obfs4 bridges.
There are two reasons:

  1. They advertise a private IP address, e.g., 10.0.0.1.
  2. Their obfs4 port is unreachable, e.g., because of NAT.

Some of these bridges have contact info and we sent at least one email
to the operator but never heard back.  The other obfs4 bridges don't
have contact info.  After implementing #28655, we no longer hand out the
vanilla line of a bridge that also supports obfs4.  Therefore, bridges
whose obfs4 port is unreachable are effectively useless.

Yahoo allows you to create up to 500 disposable email addresses, which
BridgeDB interprets as unique:
<https://bugs.torproject.org/28496#comment:8>

We could address this issue in BridgeDB but at this point we seem better
off dropping support for Yahoo because the provider likely also fell
behind in Sybil protection.

This fixes bug 28496: <https://bugs.torproject.org/28496>

This config option was introduced as part of our bug fix for
<https://bugs.torproject.org/28655>.