SIGMET error

[voynovia]

example: "WSMV31 VRMM 020506 VRMF SIGMET 2 VALID 020500/020900 VRMM- VRMF MALE FIR EMBD TS FCST WI N0524 E07800-S0215 E07748-S0600 E07500-S0600 E06807-S0007 E06800-N0457 E07000-N0524 E07800 TOP FL420 MOV E2KT INTSF="

error: "invalid literal for int() with base 10: 'E2KT'"

[devdupont]

Fix pushed in 488fe67 by updating the item length check.