Merge #11829: Test datadir specified in conf file exists
529b866 Test datadir in conf file exists (MeshCollider)
Pull request description:
Provoked by Nick ODell's discovery here: https://bitcoin.stackexchange.com/questions/64189/when-running-bitcoind-i-keep-getting-boostfilesystemspace-operation-not-p/64210#64210
If a custom data directory is specified using `-datadir` argument, its existence is checked before the conf file is loaded. But if the conf file then specifies a different non-existent `datadir`, that isn't tested, and results in esoteric errors like:
EXCEPTION: N5boost10filesystem16filesystem_errorE
boost::filesystem::space: Operation not permitted
This just adds a check for the datadir existence at the end of `ReadConfigFile()`
Tree-SHA512: e488618c40aa356263f94040ae00aa4be98038abef66e8674b01032d22a5553a7fafcb8fe2d1f095865b39fb138c07b7a94415a00ef837573f92f95af065f712