Use str.format, raise exception in name function

[ThomDietrich]

Hey,

this change tackles the eminent error as can be seen in #31 (doesn't resolve the actual issue).

• name method now raises an exception when no data could be retrieved
• Unfavorable line wrapping fixed
• string building in combination with the logger was wrong. I've replaced everything with the better str.format method e.g.

OSError: [Errno Could not read data from Mi Flora sensor %s] C4:7C:8D:60:DB:A5

[ThomDietrich]

Sorry to bother you. Any issues with this PR I should be aware of? Cheers ;)

[ghost]

logging should not use string.format
lines should be no longer than 79 characters.

[ThomDietrich]

logging should not use string.format

Okay, the bug still needs to be fixed somehow...

lines should be no longer than 79 characters

A rather archaic length. Nowadays 120 or 160 is reasonable. Anyhow that's up to you.

[ghost]

Please create a new pull request for the fix

About line length and a lot of other style guidelines, please check the PEP8 Python style gudielines:
https://www.python.org/dev/peps/pep-0008/#maximum-line-length

[ThomDietrich]

Done (#35)

I'm aware of PEP8. As I said, it's up to you.