Linter fails with OSError if multiple repos are used

Version
```
(azdev-env) frp $ azdev --version
0.1.28

Python (Darwin) 3.8.5 (default, Aug 25 2020, 13:30:25)
[Clang 11.0.3 (clang-1103.0.32.62)]
```
Configuration
```
[ext]
repo_paths = /frp/az-cli/.azdev/azure-cli-extensions,/frp

[cli]
repo_path = _NONE_
```
Command
`azdev linter livedata`

Error
```
Running pylint on extensions...
Traceback (most recent call last):
File "/.pyenv/versions/3.8.5/lib/python3.8/runpy.py", line 194, in _run_module_as_main
return _run_code(code, main_globals, None,
File ".pyenv/versions/3.8.5/lib/python3.8/runpy.py", line 87, in _run_code
exec(code, run_globals)
File "/frp/az-cli/.azdev/azdev-env/lib/python3.8/site-packages/pylint/__main__.py", line 8, in
pylint.run_pylint()
File "/frp/az-cli/.azdev/azdev-env/lib/python3.8/site-packages/pylint/__init__.py", line 20, in run_pylint
Run(sys.argv[1:])
File "/frp/az-cli/.azdev/azdev-env/lib/python3.8/site-packages/pylint/lint.py", line 1573, in __init__
linter.read_config_file(verbose=self.verbose)
File "/frp/az-cli/.azdev/azdev-env/lib/python3.8/site-packages/pylint/config.py", line 721, in read_config_file
raise IOError("The config file {:s} doesn't exist!".format(config_file))
OSError: The config file /frp/az-cli/.azdev/azure-cli-extensions,/frp/pylintrc doesn't exist!
```