pw_presubmit: Tweaks to format warnings
pw_presubmit: Tweaks to format warnings

Adds a copy-and-pastable command to fix formatting issues. Example:

$ pw presubmit
(... output omitted ...)
┏━━━━━━━━┯━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┯━━━━━━━━━━━┓
┃  14/15 │ Python format                                           │  43 files ┃
20191213 16:16:13 WRN Found 4 files with formatting errors. Format changes:

Change-Id: I9ea9058884dd32171fb7d8690ea2ffc2c2761e54
--- pw_bloat/py/bloat_output.py	(original)
+++ pw_bloat/py/bloat_output.py	(reformatted)
@@ -32,6 +32,7 @@
     @abc.abstractmethod
     def diff(self) -> str:

(... output omitted ...)

20191216 10:03:24 WRN To fix formatting, run:

  pw format --fix pw_bloat/py/bloat.py
  pw format --fix pw_bloat/py/bloat_output.py
  pw format --fix pw_presubmit/py/pw_presubmit/install_hook.py
  pw format --fix pw_protobuf_compiler/BUILD.gn

┃        │                                                         │           ┃
┃ FAILED │ Python format                                           │    0:00.5 ┃
┗━━━━━━━━┷━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┷━━━━━━━━━━━┛

Change-Id: I15a0fd442768b8af74920337eba911cc2066a80b

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