Improve Error Handling ("CLI Failed to run bridge.")

[tacerus]

Describe the bug
Upon migrating an instance of matrix-appservice-irc by importing the database and copying the configuration files over to a new system I was faced with generic errors, which were only resolvable upon analyzing the startup process with strace. I deem this not user friendly, as the errors were very easy to resolve after finding out what they are.

To Reproduce
Steps to reproduce the behavior:

1. Install the program using npm, either with or wihout a cloned git repository at hand
2. Set up a PostgreSQL database filled with data from a previous matrix-appservice-irc install
3. Make sure the npm packages color-name and color-convert are NOT installed
4. Make sure provisioning is configured in the config.yaml, but do NOT provide a provisioning.rules.yaml file in the installation directory.
5. Observe the program present you with a generic "Failed to run bridge." error message.

Expected behavior

1. The program should tell the user which npm packages are missing.
2. The program should tell the user which configuration files are missing.

Observed behavior

The program prints the following console output:

Apr 19 19:50:29 theia node[23330]: 2021-04-19 19:50:29 INFO:IrcBridge Started metrics on http://127.0.0.1:9976
Apr 19 19:50:29 theia node[23330]: 2021-04-19 19:50:29 INFO:IrcBridge Using PgDataStore for Datastore
Apr 19 19:50:29 theia node[23330]: 2021-04-19 19:50:29 INFO:CryptoStore Private key loaded from /opt/matrix/appserviceirc/passkey.pem - IRC password encryption enabled.
Apr 19 19:50:29 theia node[23330]: 2021-04-19 19:50:29 INFO:PgDatastore Starting postgres database engine
Apr 19 19:50:29 theia node[23330]: 2021-04-19 19:50:29 INFO:PgDatastore Database schema is at version v5
Apr 19 19:50:29 theia node[23330]: 2021-04-19 19:50:29 INFO:IrcServer Reconfiguring irc.liberta.casa
Apr 19 19:50:29 theia node[23330]: 2021-04-19 19:50:29 INFO:PgDatastore storeRoom (id=!kGldNYWbgjhCfxkkJI:liberta.casa, addr=irc.liberta.casa, chan=#mods, origin=config, type=channel)
Apr 19 19:50:29 theia node[23330]: 2021-04-19 19:50:29 INFO:PgDatastore storeRoom (id=!kluNNKMKtGSnRiVdpf:liberta.casa, addr=irc.liberta.casa, chan=#dev, origin=config, type=channel)
Apr 19 19:50:29 theia node[23330]: 2021-04-19 19:50:29 INFO:PgDatastore storeRoom (id=!owFmWWcNHVQbjIITNp:liberta.casa, addr=irc.liberta.casa, chan=#help, origin=config, type=channel)
Apr 19 19:50:29 theia node[23330]: 2021-04-19 19:50:29 INFO:PgDatastore storeRoom (id=!CxaPdOZSAoPLiAQzcU:liberta.casa, addr=irc.liberta.casa, chan=#annie, origin=config, type=channel)
Apr 19 19:50:29 theia node[23330]: 2021-04-19 19:50:29 INFO:PgDatastore storeRoom (id=!YpZhKgnqANeHgWkmoI:liberta.casa, addr=irc.liberta.casa, chan=#praxis, origin=config, type=channel)
Apr 19 19:50:29 theia node[23330]: 2021-04-19 19:50:29 INFO:PgDatastore storeRoom (id=!HBbrMSEerejblGhsSV:aria-net.org, addr=irc.liberta.casa, chan=#ita, origin=config, type=channel)
Apr 19 19:50:29 theia node[23330]: Apr-19 19:50:29.944 INFO room-link-validator Detected rule config change...
Apr 19 19:50:29 theia node[23330]: 2021-04-19 19:50:29 ERROR:CLI Failed to run bridge.
Apr 19 19:50:29 theia node[23330]: 2021-04-19 19:50:29 ERROR:CLI undefined

The program prints the following into the configured error logfile:
ERROR:CLI Failed to run bridge.

The program prints the following into the configured debug logfile:

INFO:IrcBridge Started metrics on http://127.0.0.1:9976
INFO:IrcBridge Using PgDataStore for Datastore
INFO:CryptoStore Private key loaded from /opt/matrix/appserviceirc/passkey.pem - IRC password encryption enabled.
INFO:PgDatastore Starting postgres database engine
INFO:PgDatastore Database schema is at version v5
INFO:IrcServer Reconfiguring irc.liberta.casa
INFO:PgDatastore storeRoom (id=!kGldNYWbgjhCfxkkJI:liberta.casa, addr=irc.liberta.casa, chan=#mods, origin=config, type=channel)
INFO:PgDatastore storeRoom (id=!kluNNKMKtGSnRiVdpf:liberta.casa, addr=irc.liberta.casa, chan=#dev, origin=config, type=channel)
INFO:PgDatastore storeRoom (id=!owFmWWcNHVQbjIITNp:liberta.casa, addr=irc.liberta.casa, chan=#help, origin=config, type=channel)
INFO:PgDatastore storeRoom (id=!CxaPdOZSAoPLiAQzcU:liberta.casa, addr=irc.liberta.casa, chan=#annie, origin=config, type=channel)
INFO:PgDatastore storeRoom (id=!YpZhKgnqANeHgWkmoI:liberta.casa, addr=irc.liberta.casa, chan=#praxis, origin=config, type=channel)
INFO:PgDatastore storeRoom (id=!HBbrMSEerejblGhsSV:aria-net.org, addr=irc.liberta.casa, chan=#ita, origin=config, type=channel)
ERROR:CLI Failed to run bridge.

Manual troubleshooting using strace

openat(AT_FDCWD, "./provisioning.rules.yaml", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)
write(17, "2021-04-19 20:01:24 ERROR:CLI Fa"..., 522021-04-19 20:01:24 ERROR:CLI Failed to run bridge.

Aha!

[jaller94]

Line in question:

matrix-appservice-irc/app.js

Line 61 in 06645e6

log.error("Failed to run bridge.");