ssh provider has limit to sshtunnel  < 0.2
https://github.com/apache/airflow/blob/9d6ae609b60449bd274c2f96e72486d73ad2b8f9/setup.py#L451

I don't know why? sshtunnel  already released 0.4
I didn't open PR because I don't know this provider i just tried to install it and couldn't due to conflicts with other requirements in my system so eventually i used vitrual env to solve my problem but logging this issue so that someone who knows this code can handle it.
setup.py
]
leveldb = ['plyvel']
mongo = [
    'dnspython>=1.13.0,<3.0.0',
    'pymongo>=3.6.0',
]
mssql = [
    'pymssql~=2.1,>=2.1.5',
]
mysql = [
    'mysql-connector-python>=8.0.11, <9',
    'mysqlclient>=1.3.6,<3',
]
neo4j = ['neo4j>=4.2.1']
odbc = [
    'pyodbc',
]
oracle = [
    'cx_Oracle>=5.1.2',
]
pagerduty = [
    'pdpyras>=4.1.2,<5',
]
pandas = [
    'pandas>=0.17.1, <2.0',
]
papermill = [
    'papermill[all]>=1.2.1',
    'scrapbook[all]',
]