common/utils fails when loading dysfunctional paramiko version
Motivation
----------
Paramiko needs to be imported in a try/except block.

diff --git a/lib/rucio/common/utils.py b/lib/rucio/common/utils.py
index 4f05f0ff1..b7677b17f 100644
--- a/lib/rucio/common/utils.py
+++ b/lib/rucio/common/utils.py
@@ -97,7 +97,10 @@ if EXTRA_MODULES['web']:
     from web import HTTPError
 
 if EXTRA_MODULES['paramiko']:
-    from paramiko import RSAKey
+    try:
+        from paramiko import RSAKey
+    except Exception:
+        EXTRA_MODULES['paramiko'] = False
 
 if EXTRA_MODULES['flask']:
     from flask import Response
@@ -660,7 +663,7 @@ def ssh_sign(private_key, message):
     :return: Base64 encoded signature as a string.
     """
     if not EXTRA_MODULES['paramiko']:
-        raise MissingModuleException('The paramiko module is not installed.')
+        raise MissingModuleException('The paramiko module is not installed or faulty.')
     sio_private_key = StringIO(private_key)
     priv_k = RSAKey.from_private_key(sio_private_key)
     sio_private_key.close()
['lib/rucio/common/utils.py']