Bump pygments from 2.5.2 to 2.7.4 in /dr

Bumps [pygments](https://github.com/pygments/pygments) from 2.5.2 to 2.7.4.
- [Release notes](https://github.com/pygments/pygments/releases)
- [Changelog](https://github.com/pygments/pygments/blob/master/CHANGES)
- [Commits](pygments/pygments@2.5.2...2.7.4)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

dr/requirements.txt

@@ -67,7 +67,7 @@ ptyprocess==0.6.0
 pyasn1==0.4.2
 pyasn1-modules==0.2.1
 pycrypto==2.6.1
-Pygments==2.2.0
+Pygments==2.7.4
 pygobject==3.26.1
 PyJWT==1.5.3
 pyOpenSSL==17.5.0