Fixup requirements.txt

Use recent version of keyrings
Remove redundant stuff
Reordering

Author: Flamefire

requirements.txt

@@ -1,34 +1,23 @@
 # keyring is required to provide GitHub token to EasyBuild;
 # for recent versions of keyring, keyrings.alt must be installed too
-keyring<=9.1
+keyring<19.0; python_version < '3.0' # 19.0 dropped Python 2 support
+keyring; python_version >= '3.0'
 keyrings.alt
 
-gitdb
+# cryptography 3.4.0 no longer supports Python 2
+cryptography==3.3.2; python_version < '3.0'
+cryptography; python_version >= '3.0'
 
 # GitPython 3.1.15 deprecates Python 3.5
 GitPython==3.1.14; python_version >= '3.0' and python_version < '3.6'
 GitPython; python_version >= '3.6' or python_version <= '3.0'
 
-
-# pydot (dep for python-graph-dot)
-pydot
-
+# flake8 is a superset of pycodestyle and depends on it (we need pycodestyle for the style tests)
+flake8
 autopep8
-
 PyYAML
-
-# optional Python packages for EasyBuild
-
-# flake8 is a superset of pycodestyle
-flake8
-
 GC3Pie
 python-graph-dot
 python-hglib
 requests
-
 archspec
-
-# cryptography 3.4.0 no longer supports Python 2.7
-cryptography==3.3.2; python_version == '2.7'
-cryptography; python_version >= '3.5'