chore(deps): bump babel from 2.8.0 to 2.9.1

Bumps [babel](https://github.com/python-babel/babel) from 2.8.0 to 2.9.1.
- [Release notes](https://github.com/python-babel/babel/releases)
- [Changelog](https://github.com/python-babel/babel/blob/master/CHANGES)
- [Commits](python-babel/babel@v2.8.0...v2.9.1)

---
updated-dependencies:
- dependency-name: babel
  dependency-type: indirect
...

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

Author: dependabot[bot]

dev-requirements.txt

@@ -8,7 +8,7 @@ alabaster==0.7.12
     # via sphinx
 attrs==19.3.0
     # via pytest
-babel==2.8.0
+babel==2.9.1
     # via sphinx
 certifi==2019.11.28
     # via requests
@@ -24,17 +24,17 @@ docutils==0.16
     # via sphinx
 entrypoints==0.3
     # via flake8
+flake8==3.7.9
+    # via
+    #   -r dev-requirements.in
+    #   flake8-polyfill
+    #   flake8-quotes
 flake8-import-order==0.18.1
     # via -r dev-requirements.in
 flake8-polyfill==1.0.2
     # via pep8-naming
 flake8-quotes==2.1.1
     # via -r dev-requirements.in
-flake8==3.7.9
-    # via
-    #   -r dev-requirements.in
-    #   flake8-polyfill
-    #   flake8-quotes
 idna==2.9
     # via requests
 imagesize==1.2.0
@@ -47,10 +47,10 @@ mccabe==0.6.1
     # via flake8
 more-itertools==8.2.0
     # via pytest
-mypy-extensions==0.4.3
-    # via mypy
 mypy==0.770
     # via -r dev-requirements.in
+mypy-extensions==0.4.3
+    # via mypy
 packaging==20.3
     # via
     #   pytest
@@ -71,12 +71,12 @@ pygments==2.7.4
     # via sphinx
 pyparsing==2.4.6
     # via packaging
-pytest-cov==2.8.1
-    # via -r dev-requirements.in
 pytest==5.4.0
     # via
     #   -r dev-requirements.in
     #   pytest-cov
+pytest-cov==2.8.1
+    # via -r dev-requirements.in
 pytz==2019.3
     # via babel
 requests==2.23.0