python3Packages.paramiko: fix build with cryptography>=3.1

pkgs/development/python-modules/paramiko/default.nix

@@ -1,6 +1,7 @@
 { pkgs
 , buildPythonPackage
 , fetchPypi
+, fetchpatch
 , cryptography
 , bcrypt
 , invoke
@@ -20,6 +21,13 @@ buildPythonPackage rec {
     sha256 = "920492895db8013f6cc0179293147f830b8c7b21fdfc839b6bad760c27459d9f";
   };
 
+  patches = [
+    # fix RSA key loading with cryptography 3.1, remove >2.7.1
+    (fetchpatch {
+      url = "https://github.com/paramiko/paramiko/commit/81064206bf3cec2ca4372257ff138481e1227b91.patch";
+      sha256 = "01b87ffgyvd6rilp1w1kf7lk29z706ch39nwl21ifklqpjhmazww";
+    })
+  ];
   checkInputs = [ invoke pytest mock pytest-relaxed ];
   propagatedBuildInputs = [ bcrypt cryptography pynacl pyasn1 ];
 
@@ -27,6 +35,7 @@ buildPythonPackage rec {
 
   # 2 sftp tests fail (skip for now)
   # test_config relies on artifacts to be to downloaded
+  # RSA tests don't have valid keys
   checkPhase = ''
     pytest tests \
       --ignore=tests/test_sftp.py \