here's the error: "Unable to initialize migration with the provided inputs. Check the log for details"
and in the log it says:
2016-02-10T17:12:10.913-07:00 ce4 E:Sql ExchangeMigration!SqliteStatement::ExecTimeout @ 715 ()> Failed to execute query: INSERT into MigrationUsers (MigrationId, Username, MigrationStatus) VALUES (?, ?, ?) error: 19 message: constraint failed
2016-02-10T17:12:10.913-07:00 ce4 E:Sql ExchangeMigration!SqliteStatement::ExecTimeout @ 716 ()> Failed with 0x80be0013, last successful line = 668.
2016-02-10T17:12:10.913-07:00 ce4 E:Sql ExchangeMigration!SqliteStatement::Exec @ 657 ()> Failed with 0x80be0013, last successful line = 656.
2016-02-10T17:12:10.913-07:00 ce4 E:Sql ExchangeMigration!SqliteStatement::Reset @ 622 ()> Failed with 0x80be0013, last successful line = 615.
2016-02-10T17:12:10.913-07:00 ce4 E:Migration ExchangeMigration!MasterMigrationDbImpl::AddMigrationUser @ 383 ()> Failed with 0x80be0013, last successful line = 382.
2016-02-10T17:12:10.913-07:00 ce4 E:Migration ExchangeMigration!ServerMigrationConfig::AddMigrationUsersToDb @ 100 ()> Failed with 0x80be0013, last successful line = 93.
2016-02-10T17:12:10.913-07:00 ce4 E:Migration ExchangeMigration!MigrationConfig::InitiateMasterDb @ 167 ()> Failed with 0x80be0013, last successful line = 164.
2016-02-10T17:12:10.913-07:00 ce4 E:Migration ExchangeMigration!MigrationMain::PrepareConfigInstanceForMigration @ 474 ()> Failed with 0x80be0013, last successful line = 468.
It turns out this error was my fault because I sloppily had a duplicate in either my 'all users' or 'subset users' list. Just clean up these two files to make sure no dupes exist and the error should go away.
