Fix - import pysftp only when necessary

Blender 2.93 has issue with conflicting libraries, pysftp is actually not needed in provider running in a host, do not import it or explode when its not necessary

openpype/modules/default_modules/sync_server/providers/sftp.py

@@ -11,11 +11,15 @@ from openpype.api import get_system_settings
 from .abstract_provider import AbstractProvider
 log = Logger().get_logger("SyncServer")
 
+pysftp = None
 try:
-    import pysftp
+    import pysftp as _pysftp
+
+    pysftp = _pysftp
 except (ImportError, SyntaxError):
-    if six.PY3:
-        six.reraise(*sys.exc_info())
+    pass
+    # if six.PY3:
+    #     six.reraise(*sys.exc_info())
 
     # handle imports from Python 2 hosts - in those only basic methods are used
     log.warning("Import failed, imported from Python 2, operations will fail.")
@@ -41,7 +45,7 @@ class SFTPHandler(AbstractProvider):
         self.project_name = project_name
         self.site_name = site_name
         self.root = None
-        self.conn = None
+        self._conn = None
 
         self.presets = presets
         if not self.presets:
@@ -63,11 +67,17 @@ class SFTPHandler(AbstractProvider):
         self.sftp_key = provider_presets["sftp_key"]
         self.sftp_key_pass = provider_presets["sftp_key_pass"]
 
-        self.conn = self._get_conn()
-
         self._tree = None
         self.active = True
 
+    @property
+    def conn(self):
+        """SFTP connection, cannot be used in all places though."""
+        if not self._conn:
+            self._conn = self._get_conn()
+
+        return self._conn
+
     def is_active(self):
         """
             Returns True if provider is activated, eg. has working credentials.
@@ -321,7 +331,8 @@ class SFTPHandler(AbstractProvider):
         if not self.file_path_exists(path):
             raise FileNotFoundError("File {} to be deleted doesn't exist."
                                     .format(path))
-        self.conn.remove(path)
+        conn = self._get_conn()
+        conn.remove(path)
 
     def list_folder(self, folder_path):
         """
@@ -394,6 +405,9 @@ class SFTPHandler(AbstractProvider):
         Returns:
             pysftp.Connection
         """
+        if not pysftp:
+            raise ImportError
+
         cnopts = pysftp.CnOpts()
         cnopts.hostkeys = None