forward pyftpdlib dependency version cap for python-2.7 from latest docker-migrid commit.

git-svn-id: svn+ssh://svn.code.sf.net/p/migrid/code/trunk@6135 b75ad72c-e7d7-11dd-a971-7dbc132099af

Author: jonasbardino

recommended.txt

@@ -27,7 +27,9 @@ email-validator<1.3;python_version < "3"
 wsgidav
 paramiko
 pyOpenSSL
-pyftpdlib
+# NOTE: python-2.7 versions require older pyftpdlib
+pyftpdlib;python_version >= "3"
+pyftpdlib<2.0;python_version < "3"
 watchdog
 scandir
 python-openid