get_interface returns -1 for speed if Auto negotiate is used on Juniper

[robobeaver6]

reproduced using Nornir to call Napalm get_interface on a Juniper EX4300 running Junos 14.1X53-D47.6

task.run(task=napalm_get,
                       name='Get Interface Details',
                       getters='get_interfaces',
                       severity_level=logging.DEBUG)

The information returned for a single up interface:

{ 'get_interfaces': { 'ge-0/0/2': { 'description': 'Phone: Desk U18 {Floorport '
                                                   '115}',
                                                 'is_enabled': True,
                                                 'is_up': True,
                                                 'last_flapped': 4562584.0,
                                                 'mac_address': 'C0:42:D0:C5:0A:25',
                                                 'speed': -1},
}

I believe napalm is resolving the speed as Auto from the show interface command (or something similar).

rhall@loonaccess52> show interfaces ge-0/0/2 
Physical interface: ge-0/0/2, Enabled, Physical link is Up
  Interface index: 663, SNMP ifIndex: 512
  Description: Phone: Desk U18 {Floorport 115}
  Link-level type: Ethernet, MTU: 1514, MRU: 0, Link-mode: Full-duplex, Speed: Auto, BPDU Error: None, MAC-REWRITE Error: None, Loopback: Disabled, Source filtering: Disabled,
  Flow control: Enabled, Auto-negotiation: Enabled, Remote fault: Online, Media type: Copper, IEEE 802.3az Energy Efficient Ethernet: Disabled
  Device flags   : Present Running
  Interface flags: SNMP-Traps Internal: 0x0
  Link flags     : None
  CoS queues     : 12 supported, 12 maximum usable queues
  Current address: c0:42:d0:c5:0a:25, Hardware address: c0:42:d0:c5:0a:25
  Last flapped   : 2019-01-18 19:48:05 UTC (7w3d 19:29 ago)
  Input rate     : 0 bps (0 pps)
  Output rate    : 256 bps (1 pps)
  Active alarms  : None
  Active defects : None
  Interface transmit statistics: Disabled

  Logical interface ge-0/0/2.0 (Index 581) (SNMP ifIndex 517)
    Flags: Up SNMP-Traps 0x0 Encapsulation: Ethernet-Bridge
    Input packets : 80784
    Output packets: 167464
    Protocol eth-switch, MTU: 1514

if the command show interface media were used, the response would contain the auto negotiation information, including the speed

rhall@loonaccess52> show interfaces ge-0/0/2 media 
Physical interface: ge-0/0/2, Enabled, Physical link is Up
  Interface index: 663, SNMP ifIndex: 512
  Description: Phone: Desk U18 {Floorport 115}
  Link-level type: Ethernet, MTU: 1514, MRU: 0, Link-mode: Full-duplex, Speed: Auto, BPDU Error: None, MAC-REWRITE Error: None, Loopback: Disabled, Source filtering: Disabled,
  Flow control: Enabled, Auto-negotiation: Enabled, Remote fault: Online, Media type: Copper, IEEE 802.3az Energy Efficient Ethernet: Disabled
  Device flags   : Present Running
  Interface flags: SNMP-Traps Internal: 0x0
  Link flags     : None
  CoS queues     : 12 supported, 12 maximum usable queues
  Current address: c0:42:d0:c5:0a:25, Hardware address: c0:42:d0:c5:0a:25
  Last flapped   : 2019-01-18 19:48:05 UTC (7w3d 19:31 ago)
  Input rate     : 74240 bps (43 pps)
  Output rate    : 45792 bps (29 pps)
  Active alarms  : None
  Active defects : None
  MAC statistics:
    Input bytes: 877854914, Input packets: 4058264, Output bytes: 878718262, Output packets: 6956180
  Autonegotiation information:
    Negotiation status: Complete
    Link partner:
        Link mode: Full-duplex, Flow control: None, Remote fault: OK, Link partner Speed: 100 Mbps
    Local resolution:
        Flow control: None, Remote fault: Link OK, Local link Speed: 100 Mbps, Link mode: Full-duplex
  Interface transmit statistics: Disabled

This issue does not occur on ten gig interface, as the speed does not show as Auto.

[robobeaver6]

Forgot to say the versions:
napalm 2.3.1
nornir 2.0.0