用的是eclipse之前在官网下了一个，编译AT-firmware固件是总是提示下面的错误，后来又在其它地方下了一个，可以编译成功，但不知道什么原因今天又不行了。
File "../tools/mod_esptool.py", line 22, in <module>
import serial
ImportError: No module named serial
../Makefile:86: recipe for target '.output/eagle/debug/bin/eagle.app.v6.bin' failed
make[1]: Leaving directory '/cygdrive/d/ESP8266_TOOLS/AITHINKER-ESP8266-SDK/project/at-firmware/app'
make[1]: *** [.output/eagle/debug/bin/eagle.app.v6.bin] Error 1
Makefile:106: recipe for target '.subdirs' failed
make: *** [.subdirs] Error 2
File "../tools/mod_esptool.py", line 22, in <module>
import serial
ImportError: No module named serial
../Makefile:86: recipe for target '.output/eagle/debug/bin/eagle.app.v6.bin' failed
make[1]: Leaving directory '/cygdrive/d/ESP8266_TOOLS/AITHINKER-ESP8266-SDK/project/at-firmware/app'
make[1]: *** [.output/eagle/debug/bin/eagle.app.v6.bin] Error 1
Makefile:106: recipe for target '.subdirs' failed
make: *** [.subdirs] Error 2
