OK, this *does* happen without Console.app open as well.
But I think the Console.app occurrences are related to this error in the system.log file:
21/10/15 13:13:52,003 Console[492]: Failed to connect (_consoleX) outlet from (NSApplication) to (ConsoleX): missing setter or instance variable
21/10/15 13:13:52,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:52,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:52,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:52,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:52,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:52,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:52,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:52,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:52,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
It could be a co-incidence, but from the log it appears as if the iMac wanted to return from sleeping:
21/10/15 12:56:50,721 WindowServer[158]: device_generate_desktop_screenshot: authw 0x7fd7ca95fc00(2000), shield 0x7fd7ca135a00(2001)
21/10/15 12:56:50,721 WindowServer[158]: device_generate_lock_screen_screenshot: authw 0x7fd7ca95fc00(2000)[0, 0, 0, 0] shield 0x7fd7ca135a00(2001), dev [2560,1440]
21/10/15 12:56:50,721 WindowServer[158]: no sleep images for WillPowerOffWithImages
21/10/15 12:57:00,403 loginwindow[88]: CoreAnimation: warning, deleted thread with uncommitted CATransaction; set CA_DEBUG_TRANSACTIONS=1 in environment to log backtraces.
21/10/15 12:57:59,204 ntpd[181]: drift PPM:0.000 -> -48.853
21/10/15 13:01:49,000 syslogd[41]: ASL Sender Statistics
21/10/15 13:01:57,009 CommCenter[255]: Telling CSI to go low power.
21/10/15 13:01:57,009 AirPlayUIAgent[319]: 2015-10-21 01:01:57.009004 PM [AirPlayUIAgent] BecomingInactive: NSWorkspaceWillSleepNotification
21/10/15 13:02:12,097 powerd[50]: BUG in libdispatch: 15A284 - 1631 - 0x0
21/10/15 13:02:12,000 kernel[0]: IOCTL not recognized: 234 out of 235
21/10/15 13:02:12,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:02:12,000 kernel[0]: IOCTL not recognized: 234 out of 235
21/10/15 13:02:13,000 kernel[0]: PM response took 1004 ms (50, powerd)
21/10/15 13:02:13,000 kernel[0]: en1: 802.11d country code set to 'X3'.
21/10/15 13:02:13,000 kernel[0]: en1: Supported channels 1 2 3 4 5 6 7 8 9 10 11 12 13 36 40 44 48 52 56 60 64 100 104 108 112 116 120 124 128 132 136 140
21/10/15 13:02:13,000 kernel[0]: kern_open_file_for_direct_io(0)
21/10/15 13:02:13,000 kernel[0]: kern_open_file_for_direct_io took 0 ms
21/10/15 13:02:13,000 kernel[0]: Opened file /var/log/SleepWakeStacks.bin, size 180224, extents 1, maxio 2000000 ssd 0
21/10/15 13:02:13,000 kernel[0]: polled file major 1, minor 0, blocksize 4096, pollers 0
21/10/15 13:02:13,000 kernel[0]: ARPT: 2460.927084: AirPort_Brcm43xx::powerChange: System Sleep
21/10/15 13:02:13,000 kernel[0]: ARPT: 2461.429099: IOPMPowerSource Information: onSleep, SleepType: Normal Sleep,
21/10/15 13:02:13,000 kernel[0]: ARPT: 2461.429120: wl0: powerChange: *** BONJOUR/MDNS OFFLOADS ARE NOT RUNNING.
21/10/15 13:02:13,000 kernel[0]: en1: channel changed to 1
21/10/15 13:02:13,000 kernel[0]: AirPort: Link Down on awdl0. Reason 1 (Unspecified).
21/10/15 13:02:13,000 kernel[0]: ARPT: 2461.470461: AirPort_Brcm43xx::syncPowerState: WWEN[disabled]
21/10/15 13:02:13,000 kernel[0]: in6_unlink_ifa: IPv6 address 0xff19293e6f86517 has no prefix
21/10/15 13:02:13,000 kernel[0]: Bluetooth -- LE is supported - Disable LE meta event
21/10/15 13:02:13,000 kernel[0]: AppleBCM5701Ethernet [en0]: Link down (womp enabled, proxy idle)
21/10/15 13:02:14,000 kernel[0]: AppleThunderboltNHIType2::waitForOk2Go2Sx - retries = 108
21/10/15 13:13:07,000 kernel[0]: Wake reason: EHC1
21/10/15 13:13:07,000 syslogd[41]: ASL Sender Statistics
21/10/15 13:13:07,000 kernel[0]: Previous sleep cause: 5
21/10/15 13:13:07,000 kernel[0]: AppleThunderboltNHIType2::prePCIWake - power up complete - took 2 us
21/10/15 13:13:07,000 kernel[0]: Sandbox: mDNSResponder(85) deny(1) mach-lookup com.apple.distributed_notifications@1v3
21/10/15 13:13:07,000 kernel[0]: full wake promotion (reason 1) 74 ms
21/10/15 13:13:07,074 CommCenter[255]: Telling CSI to exit low power.
21/10/15 13:13:07,000 kernel[0]: IOThunderboltSwitch<0>(0x0)::listenerCallback - Thunderbolt HPD packet for route = 0x0 port = 11 unplug = 0
21/10/15 13:13:07,000 kernel[0]: IOThunderboltSwitch<0>(0x0)::listenerCallback - Thunderbolt HPD packet for route = 0x0 port = 12 unplug = 0
21/10/15 13:13:07,000 kernel[0]: NVRM: 0x702a called in D3
21/10/15 13:13:07,000 kernel[0]: en1: channel changed to 1
21/10/15 13:13:07,000 kernel[0]: IO80211AWDLPeerManager::getVHtCapabilityIE Unable to get vht capabilities ret 2d
21/10/15 13:13:07,207 airportd[55]: _bsd_80211_event_callback: Failed to get power setting from device : err -3900
21/10/15 13:13:07,210 Dock[244]: -[UABestAppSuggestionManager notifyBestAppChanged:type:options:bundleIdentifier:activityType:dynamicIdentifier:when:confidence:deviceName:deviceIdentifier:deviceType:] (null) UASuggestedActionType=0 (null)/(null) opts=(null) when=2015-10-21 11:13:07 +0000 confidence=1 from=(null)/(null) (UABestAppSuggestionManager.m #319)
21/10/15 13:13:07,000 kernel[0]: AirPort: Link Up on awdl0
21/10/15 13:13:07,000 kernel[0]: IOThunderboltSwitch<0>(0x0)::listenerCallback - Thunderbolt HPD packet for route = 0x0 port = 4 unplug = 0
21/10/15 13:13:07,000 kernel[0]: IOThunderboltSwitch<0>(0x0)::listenerCallback - Thunderbolt HPD packet for route = 0x0 port = 3 unplug = 0
21/10/15 13:13:07,000 kernel[0]: IOThunderboltSwitch<0>(0x3)::listenerCallback - Thunderbolt HPD packet for route = 0x3 port = 11 unplug = 0
21/10/15 13:13:07,000 kernel[0]: IOThunderboltSwitch<0>(0x3)::listenerCallback - Thunderbolt HPD packet for route = 0x3 port = 2 unplug = 0
21/10/15 13:13:07,000 kernel[0]: IOThunderboltSwitch<0>(0x3)::listenerCallback - Thunderbolt HPD packet for route = 0x3 port = 12 unplug = 0
21/10/15 13:13:07,000 kernel[0]: TBT W (2): 0x0100 [x]
21/10/15 13:13:07,000 kernel[0]: AppleThunderboltGenericHAL::earlyWake - complete - took 737 milliseconds
21/10/15 13:13:07,000 kernel[0]: [ PCI configuration begin ]
21/10/15 13:13:07,000 kernel[0]: [ PCI configuration end, bridges 17, devices 17 ]
21/10/15 13:13:07,858 hidd[92]: [HID] [MT] MTSimpleHIDManager::deviceDidBootload device bootloaded
21/10/15 13:13:07,936 WindowServer[158]: CGXDisplayDidWakeNotification [2463596520499]: posting kCGSDisplayDidWake
21/10/15 13:13:07,936 WindowServer[158]: handle_will_sleep_auth_and_shield_windows: Reordering authw 0x7fd7ca95fc00(2004) (lock state: 3)
21/10/15 13:13:07,936 WindowServer[158]: handle_will_sleep_auth_and_shield_windows: err 0x0
21/10/15 13:13:07,994 hidd[92]: [HID] [MT] MTSimpleHIDManager::deviceDidBootload device bootloaded
21/10/15 13:13:08,039 identityservicesd[269]: <IMMacNotificationCenterManager: 0x7fae9c015f80>: notification observer: com.apple.iChat notification: __CFNotification 0x7fae9c013f50 {name = _NSDoNotDisturbDisabledNotification}
21/10/15 13:13:08,050 identityservicesd[269]: <IMMacNotificationCenterManager: 0x7fae9c015f80>: NC Disabled: NO
21/10/15 13:13:08,054 identityservicesd[269]: <IMMacNotificationCenterManager: 0x7fae9c015f80>: DND Enabled: NO
21/10/15 13:13:08,054 identityservicesd[269]: <IMMacNotificationCenterManager: 0x7fae9c015f80>: Updating enabled: YES (Topics: (
))
21/10/15 13:13:10,000 kernel[0]: Ethernet [AppleBCM5701Ethernet]: Link up on en0, 1-Gigabit, Full-duplex, Symmetric flow-control, EEE enabled, Debug [796d,0301,05e1,0200,c5e1,3800]
21/10/15 13:13:10,000 kernel[0]: in6_unlink_ifa: IPv6 address 0xff19293e6f863c7 has no prefix
21/10/15 13:13:10,737 configd[49]: LINKLOCAL en0: parent has no IP
21/10/15 13:13:10,743 configd[49]: network changed: v4(en0-:192.168.2.52) DNS- Proxy-
21/10/15 13:13:10,754 configd[49]: network changed: v4(en0+:192.168.2.52) DNS+ Proxy+ SMB
21/10/15 13:13:25,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:26,000 kernel[0]: ARPT: 2482.005896: AirPort_Brcm43xx::powerChange: System Wake - Full Wake/ Dark Wake / Maintenance wake
21/10/15 13:13:26,000 kernel[0]: ARPT: 2482.506922: IOPMPowerSource Information: onWake, SleepType: Normal Sleep,
21/10/15 13:13:26,000 kernel[0]: ARPT: 2482.507051: AirPort_Brcm43xx::platformWoWEnable: WWEN[disable]
21/10/15 13:13:26,849 sharingd[260]: 13:13:26.849 : Starting AirDrop server for user 501 on wake
21/10/15 13:13:26,000 kernel[0]: en1: channel changed to 1
21/10/15 13:13:26,000 kernel[0]: IO80211AWDLPeerManager::getVHtCapabilityIE Unable to get vht capabilities ret 2d
21/10/15 13:13:26,860 airportd[55]: _bsd_80211_event_callback: Failed to get power setting from device : err -3900
21/10/15 13:13:27,883 ntpd[181]: wake time set +0.540378 s
21/10/15 13:13:52,003 Console[492]: Failed to connect (_consoleX) outlet from (NSApplication) to (ConsoleX): missing setter or instance variable
21/10/15 13:13:52,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:52,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:52,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:52,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:52,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:52,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:52,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:52,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:52,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:52,000 kernel[0]: pci pause: SDXC
21/10/15 13:13:53,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:53,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:54,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:54,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:55,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:55,000 kernel[0]: hfs_clonefile: cluster_read failed - 34
21/10/15 13:13:56,000 kernel[0]: hfs_clonefile: cluster_read failed - 34