fabricを用いて$fab -H hoge -- uname -nとするとParamikoのエラーが出てきます．

~/.ssh/configに

Host hoge
  HostName     192.168.xxx.xxx
  Port         22
  User         pi
  IdentityFile ~/.ssh/id_rsa

とし，コマンドラインにて

$ fab -H hoge -- uname -n

を実行したところ

Traceback (most recent call last):
  File "/Users/s_o813/anaconda3/bin/fab", line 10, in <module>
    sys.exit(program.run())
  File "/Users/s_o813/anaconda3/lib/python3.7/site-packages/invoke/program.py", line 384, in run
    self.execute()
  File "/Users/s_o813/anaconda3/lib/python3.7/site-packages/invoke/program.py", line 566, in execute
    executor.execute(*self.tasks)
  File "/Users/s_o813/anaconda3/lib/python3.7/site-packages/invoke/executor.py", line 129, in execute
    result = call.task(*args, **call.kwargs)
  File "/Users/s_o813/anaconda3/lib/python3.7/site-packages/invoke/tasks.py", line 127, in __call__
    result = self.body(*args, **kwargs)
  File "/Users/s_o813/anaconda3/lib/python3.7/site-packages/fabric/executor.py", line 91, in anonymous
    c.run(self.core.remainder)
  File "<decorator-gen-3>", line 2, in run
  File "/Users/s_o813/anaconda3/lib/python3.7/site-packages/fabric/connection.py", line 29, in opens
    self.open()
  File "/Users/s_o813/anaconda3/lib/python3.7/site-packages/fabric/connection.py", line 634, in open
    self.client.connect(**kwargs)
  File "/Users/s_o813/anaconda3/lib/python3.7/site-packages/paramiko/client.py", line 446, in connect
    passphrase,
  File "/Users/s_o813/anaconda3/lib/python3.7/site-packages/paramiko/client.py", line 764, in _auth
    raise saved_exception
  File "/Users/s_o813/anaconda3/lib/python3.7/site-packages/paramiko/client.py", line 735, in _auth
    filename, pkey_class, passphrase
  File "/Users/s_o813/anaconda3/lib/python3.7/site-packages/paramiko/client.py", line 586, in _key_from_filepath
    key = klass.from_private_key_file(key_path, password)
  File "/Users/s_o813/anaconda3/lib/python3.7/site-packages/paramiko/pkey.py", line 206, in from_private_key_file
    key = cls(filename=filename, password=password)
  File "/Users/s_o813/anaconda3/lib/python3.7/site-packages/paramiko/rsakey.py", line 55, in __init__
    self._from_private_key_file(filename, password)
  File "/Users/s_o813/anaconda3/lib/python3.7/site-packages/paramiko/rsakey.py", line 175, in _from_private_key_file
    data = self._read_private_key_file("RSA", filename, password)
  File "/Users/s_o813/anaconda3/lib/python3.7/site-packages/paramiko/pkey.py", line 279, in _read_private_key_file
    data = self._read_private_key(tag, f, password)
  File "/Users/s_o813/anaconda3/lib/python3.7/site-packages/paramiko/pkey.py", line 329, in _read_private_key
    raise PasswordRequiredException("Private key file is encrypted")
paramiko.ssh_exception.PasswordRequiredException: Private key file is encrypted

というようなエラーが出ました．
paramikoは使っていないはずなのになぜこのようなエラーが出るのでしょうか？
また，原因がわかりません．
なお，RSAはこちらの記事を参考にして