Fix random CI errors #1246

  ✓ Flake8 (1189ms)
    ✓ Pep8 (1860ms)
    ✓ Pydocstyle (958ms)
Python Extension: Failed to parse pydocstyle line 'Error in file /home/travis/build/Microsoft/vscode-python/src/test/pythonFiles/linting/pylintconfig/file2.py: Cannot parse file.undefined' TypeError: Cannot read property 'length' of undefined
    at t._lineAt (/home/travis/build/Microsoft/vscode-python/.vscode-test/stable/VSCode-linux-x64/resources/app/out/vs/workbench/node/extensionHostProcess.js:482:281)
    at Object.lineAt (/home/travis/build/Microsoft/vscode-python/.vscode-test/stable/VSCode-linux-x64/resources/app/out/vs/workbench/node/extensionHostProcess.js:480:877)
    at outputLines.filter.map.map.line (/home/travis/build/Microsoft/vscode-python/out/client/linters/pydocstyle.js:9:5073)
    at Array.map (native)
    at PyDocStyle.<anonymous> (/home/travis/build/Microsoft/vscode-python/out/client/linters/pydocstyle.js:9:4366)
    at Generator.next (<anonymous>)
    at /home/travis/build/Microsoft/vscode-python/out/client/linters/pydocstyle.js:9:1515
    at Promise (<anonymous>)
    at __awaiter (/home/travis/build/Microsoft/vscode-python/out/client/linters/pydocstyle.js:9:327)
    at PyDocStyle.parseMessages (/home/travis/build/Microsoft/vscode-python/out/client/linters/pydocstyle.js:9:2964)
    ✓ PyLint with config in root (1338ms)
    ✓ Flake8 with config in root (1462ms)
    ✓ Pep8 with config in root (737ms)
Python Extension: Failed to parse pydocstyle line 'Error in file /home/travis/build/Microsoft/vscode-python/src/test/pythonFiles/linting/pydocstyleconfig27/file.py: Cannot parse file.undefined' TypeError: Cannot read property 'length' of undefined
    at t._lineAt (/home/travis/build/Microsoft/vscode-python/.vscode-test/stable/VSCode-linux-x64/resources/app/out/vs/workbench/node/extensionHostProcess.js:482:281)
    at Object.lineAt (/home/travis/build/Microsoft/vscode-python/.vscode-test/stable/VSCode-linux-x64/resources/app/out/vs/workbench/node/extensionHostProcess.js:480:877)
    at outputLines.filter.map.map.line (/home/travis/build/Microsoft/vscode-python/out/client/linters/pydocstyle.js:9:5073)
    at Array.map (native)
    at PyDocStyle.<anonymous> (/home/travis/build/Microsoft/vscode-python/out/client/linters/pydocstyle.js:9:4366)
    at Generator.next (<anonymous>)
    at /home/travis/build/Microsoft/vscode-python/out/client/linters/pydocstyle.js:9:1515
    at Promise (<anonymous>)
    at __awaiter (/home/travis/build/Microsoft/vscode-python/out/client/linters/pydocstyle.js:9:327)
    at PyDocStyle.parseMessages (/home/travis/build/Microsoft/vscode-python/out/client/linters/pydocstyle.js:9:2964)
    ✓ Pydocstyle with config in root (907ms)
    ✓ PyLint minimal checkers (6181ms)
    ✓ Multiple linters (17084ms)