Arduino 1.8.9 cannot install Esp8266

Development Tools IDE 1.x
1

Please help me this problem
I've shown: File → Preferences, enter the textbox Additional Board Manager URLs add the following link: http://arduino.esp8266.com/stable/package_esp8266com_index.json
Then go to Tool → Board → Boards Manager then get the following message:

Skipping contributed index file C:\Users\hoacv\AppData\Local\Arduino15\package_esp8266com_index.json, parsing error occured:
com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'Dropping': was expecting ('true', 'false' or 'null')
 at [Source: (FileInputStream); line: 1, column: 10]
Skipping contributed index file C:\Users\hoacv\AppData\Local\Arduino15\package_esp8266com_index.json, parsing error occured:
com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'Dropping': was expecting ('true', 'false' or 'null')
 at [Source: (FileInputStream); line: 1, column: 10]
2

hoacvxd:
Please help me this problem
I've shown: File → Preferences, enter the textbox Additional Board Manager URLs add the following link: http://arduino.esp8266.com/stable/package_esp8266com_index.json
Then go to Tool → Board → Boards Manager then get the following message:

+1

3

The problem has been reported to the ESP8266 core for Arduino's maintainers and they are working on fixing it:

4

Thanks :o

A temp workaround:

delete the lines at the top of the file before the opening {

And then only install version 2.5.0 (2.5.1 seems to break)