Bump pycparser from 2.19 to 2.20

Bumps [pycparser](https://github.com/eliben/pycparser) from 2.19 to 2.20.
- [Release notes](https://github.com/eliben/pycparser/releases)
- [Changelog](https://github.com/eliben/pycparser/blob/master/CHANGES)
- [Commits](eliben/pycparser@release_v2.19...release_v2.20)

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

requirements.txt

@@ -22,7 +22,7 @@ plaster-pastedeploy==0.7
 prettytable==0.7.2
 pyasn1==0.4.8
 pyasn1-modules==0.2.8
-pycparser==2.19
+pycparser==2.20
 pyramid==1.10.4
 pyramid-multiauth==0.9.0
 pyramid-tm==2.4