Python 3.9 shuffled the exception hierarchy, have to look for IOError, OSError one of which is common parent of both hierarchies

The change should've been API compatible, so that's not the reason for failing PR

https://docs.python.org/3.9/library/socket.html#socket.error

Author: jiridanek

.travis.yml

@@ -74,6 +74,7 @@ jobs:
     - sudo apt-get update
     - sudo apt-get install python3.9 python3.9-dev python3.9-distutils
     - sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.9 10
+    - sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.9 10
     # https://github.com/pypa/virtualenv/issues/1740
     # https://github.com/pypa/virtualenv/issues/1873
     - python -m pip install --user --upgrade pip
@@ -127,6 +128,7 @@ jobs:
       - sudo apt-get update
       - sudo apt-get install python3.9 python3.9-dev python3.9-distutils
       - sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.9 10
+      - sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.9 10
       # Install and use the latest Node.js LTS version
       - nvm install "lts/*"
       # https://github.com/pypa/virtualenv/issues/1740
@@ -158,6 +160,7 @@ jobs:
       - sudo apt-get update
       - sudo apt-get install python3.9 python3.9-dev python3.9-distutils
       - sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.9 10
+      - sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.9 10
       # https://github.com/pypa/virtualenv/issues/1740
       # https://github.com/pypa/virtualenv/issues/1873
       - python -m pip install --user --upgrade pip