trivial: Use implicit string concatenation

trivial: Use implicit string concatenation

While pycodestyle's W504 ("line break after binary operator") error was
recently disabled, it did highlight a number of areas where explicit
string concatenation was being used despite it not be necessary. Fix
these while we're aware of them.

[1] http://pycodestyle.pycqa.org/en/latest/intro.html#error-codes

Signed-off-by: Stephen Finucane <stephen@that.guru>