Platform you are automating: Android
Appium version: 1.8.0
Simulator/Emulator or Real Device: Emulator platformName=Android, platformVersion=7.1.1
The language you are using for writing tests (client binding): English I guess
Your OS: macOS Sierra 10.12.6 (16G1314)

My problem
Since Appium 1.8.0. I’m getting:
InvalidSelectorException: Message: Locator Strategy ‘css selector’ is not supported for this session
Using this:
Element Should Be Visible id=${appPackageMyPackage}:id/rowTitle

This worked fine in Appium 1.6.1 or 1.7.2

I found a temporary workaround:

1. npm uninstall -g appium
2. npm install -g appium@1.7.2 --no-shrinkwrap

I hope this will be fixed in 1.8.0