Few small fixes and improvements

[dlenski]

• Capitalization/punctuation

• Missed an f in this f-string

• Need to be able to handle empty 'SPEC' values, and ignore empty 'FIRMID', 'FIRMVER' values

  My printer's SNMP details have an empty value for 'SPEC' (which needs to be parsed correctly for the firmware downloader), but also a pair of empty values for 'FIRMID'/'FIRMVER' (at the end of the list), which need to be ignored by the firmware downloader:

  $ snmpwalk -v 2c -c public 192.168.1.123 iso.3.6.1.4.1.2435.2.4.3.99.3.1.6.1.2
  iso.3.6.1.4.1.2435.2.4.3.99.3.1.6.1.2.1 = STRING: "MODEL=\"AB-1234 series\""
  iso.3.6.1.4.1.2435.2.4.3.99.3.1.6.1.2.2 = STRING: "SERIAL=\"A1B123456\""
  iso.3.6.1.4.1.2435.2.4.3.99.3.1.6.1.2.3 = STRING: "SPEC=\"\""
  iso.3.6.1.4.1.2435.2.4.3.99.3.1.6.1.2.4 = STRING: "FIRMID=\"MAIN\""
  iso.3.6.1.4.1.2435.2.4.3.99.3.1.6.1.2.5 = STRING: "FIRMVER=\"1.18\""
  iso.3.6.1.4.1.2435.2.4.3.99.3.1.6.1.2.6 = STRING: "FIRMID=\"BRNET\""
  iso.3.6.1.4.1.2435.2.4.3.99.3.1.6.1.2.7 = STRING: "FIRMVER=\"1.04\""
  iso.3.6.1.4.1.2435.2.4.3.99.3.1.6.1.2.8 = STRING: "FIRMID=\"\""
  iso.3.6.1.4.1.2435.2.4.3.99.3.1.6.1.2.9 = STRING: "FIRMVER=\"\""
  iso.3.6.1.4.1.2435.2.4.3.99.3.1.6.1.2.10 = STRING: "                                                    "
  iso.3.6.1.4.1.2435.2.4.3.99.3.1.6.1.2.11 = STRING: "                                                    "
  iso.3.6.1.4.1.2435.2.4.3.99.3.1.6.1.2.12 = STRING: "                                                    "
  iso.3.6.1.4.1.2435.2.4.3.99.3.1.6.1.2.13 = STRING: "                                                    "
  iso.3.6.1.4.1.2435.2.4.3.99.3.1.6.1.2.14 = STRING: "                                                    "
  iso.3.6.1.4.1.2435.2.4.3.99.3.1.6.1.2.15 = STRING: "                                                    "
  iso.3.6.1.4.1.2435.2.4.3.99.3.1.6.1.2.16 = STRING: "                                                    "

  This change addresses both.

• Report host OS when downloading firmware, and allow user to override with --os

  I'm not 100% sure if it ever makes a difference, but it seems like the host OS should be reported accurately when downloading firmware. However, since its purpose is unclear it may be useful to give the user an option to override.

  Currently, the OS options are 'WINDOWS', 'MAC', or 'LINUX', since those seem to be the three OS categories which Brother's website reports support for.

• Make zeroconf dependency optional

• Apply black

[sedrubal]

Did you test the tool with a model other than the listed ones in the readme? If this is the case, we could add your model to the list.

[dlenski]

Yep, I tested with Brother HL-5370DW and it works fine for the "main" firmware file, although didn't find the update that allegedly exists for the "brnet" firmware. However, I'm fairly certain that's a mistake by Brother, not an issue with this tool.