Bump bottle from 0.12.18 to 0.12.20

Bumps [bottle](https://github.com/bottlepy/bottle) from 0.12.18 to 0.12.20.
- [Release notes](https://github.com/bottlepy/bottle/releases)
- [Changelog](https://github.com/bottlepy/bottle/blob/master/docs/changelog.rst)
- [Commits](https://github.com/bottlepy/bottle/compare/0.12.18...0.12.20)

---
updated-dependencies:
- dependency-name: bottle
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

@@ -1,4 +1,4 @@
-bottle==0.12.18
+bottle==0.12.20
 certifi==2019.11.28
 chardet==3.0.4
 Click==7.0