I tried again except this time, I deleted everything in
/var/folders/zz/* and then rebooting:
sudo rm -rf /var/folders/zz/*
Then looking at the /var/log/
tail -f /var/log/install.log
Clicking on Update of Command Line Tools (OS X 10.10) for Xcode 7.0
Sep 21 18:52:09 C02KM0AWFFT4.corp.proofpoint.com installd[2817]: installd: Starting
Sep 21 18:52:09 C02KM0AWFFT4.corp.proofpoint.com installd[2817]: installd: uid=0, euid=0
Sep 21 18:52:09 C02KM0AWFFT4.corp.proofpoint.com installd[2817]: PackageKit: Adding client PKInstallDaemonClient pid=995, uid=447226243 (/System/Library/PrivateFrameworks/CommerceKit.framework/Versions/A/Resources/s toreassetd)
Sep 21 18:52:09 C02KM0AWFFT4.corp.proofpoint.com storeassetd[995]: SUAppStoreUpdateController: authorize
Sep 21 18:52:09 C02KM0AWFFT4.corp.proofpoint.com installd[2817]: PackageKit: Adding client PKInstallDaemonClient pid=656, uid=200 (/System/Library/CoreServices/Software Update.app/Contents/Resources/softwareupdated)
Sep 21 18:52:09 --- last message repeated 1 time ---
Sep 21 18:52:09 C02KM0AWFFT4.corp.proofpoint.com storeassetd[995]: SUAppStoreUpdateController: disk space required for updates is: 1983419680
Sep 21 18:52:09 C02KM0AWFFT4.corp.proofpoint.com installd[2817]: PackageKit: Removing client PKInstallDaemonClient pid=656, uid=200 (/System/Library/CoreServices/Software Update.app/Contents/Resources/softwareupdated)
Sep 21 18:52:09 C02KM0AWFFT4.corp.proofpoint.com softwareupdated[656]: Adding client SUUpdateServiceClient pid=1535, uid=447226243, installAuth=NO rights=(), transactions=0 (/System/Library/PrivateFrameworks/CommerceKit.framework/Versions/A/Resources/L aterAgent.app/Contents/MacOS/LaterAgent)
Then clicking on Accept of agreement
Sep 21 18:52:15 C02KM0AWFFT4.corp.proofpoint.com softwareupdated[656]: Adding client SUUpdateServiceClient pid=995, uid=447226243, installAuth=NO rights=(), transactions=0 (/System/Library/PrivateFrameworks/CommerceKit.framework/Versions/A/Resources/s toreassetd)
Sep 21 18:52:15 C02KM0AWFFT4.corp.proofpoint.com storeassetd[995]: SUAppStoreUpdateController: start install session with 031-10481
Sep 21 18:52:15 C02KM0AWFFT4.corp.proofpoint.com softwareupdated[656]: SoftwareUpdate: Added foreground transaction [0x1] for Command Line Tools (OS X 10.10) for Xcode-7.0
Sep 21 18:52:15 C02KM0AWFFT4.corp.proofpoint.com softwareupdated[656]: SoftwareUpdate: starting download of 031-10481 (Command Line Tools (OS X 10.10) for Xcode-7.0)
Sep 21 18:52:16 C02KM0AWFFT4.corp.proofpoint.com softwareupdated[656]: ContentLocator: Modified URL is: http://10.20.7.131:49512/content/downloads/44/09/031-10481/jevfmj4fnqatxdq63tnq9 q1h1w8121067f/CLTools_Executables.pkg?source=swcdn.apple.com
Sep 21 18:52:16 C02KM0AWFFT4.corp.proofpoint.com softwareupdated[656]: ContentLocator: Modified URL is: http://10.20.7.131:49512/content/downloads/44/09/031-10481/jevfmj4fnqatxdq63tnq9 q1h1w8121067f/DevSDK_OSX1010.pkg?source=swcdn.apple.com
Sep 21 18:52:16 C02KM0AWFFT4.corp.proofpoint.com softwareupdated[656]: Finished downloading package CLTools_Executables.pkg to file:///var/folders/zz/zyxvpxvq6csfxvn_n00000s0000068/C/com.apple.SoftwareUpdat e/CFNetworkDownload_pqlhiI.tmp (error (null))
Sep 21 18:52:16 C02KM0AWFFT4.corp.proofpoint.com softwareupdated[656]: 031-10481: Failed post-download size check for package "CLTools_Executables.pkg": expected 125545871, got 474
Sep 21 18:52:16 C02KM0AWFFT4.corp.proofpoint.com softwareupdated[656]: Finished downloading package DevSDK_OSX1010.pkg to file:///var/folders/zz/zyxvpxvq6csfxvn_n00000s0000068/C/com.apple.SoftwareUpdat e/CFNetworkDownload_EBAY9f.tmp (error (null))
Sep 21 18:52:16 C02KM0AWFFT4.corp.proofpoint.com softwareupdated[656]: 031-10481: Failed post-download size check for package "DevSDK_OSX1010.pkg": expected 36257169, got 469
Sep 21 18:52:16 C02KM0AWFFT4.corp.proofpoint.com softwareupdated[656]: No more tasks - invalidating session now
Sep 21 18:52:16 C02KM0AWFFT4.corp.proofpoint.com softwareupdated[656]: SoftwareUpdate: finished download of 031-10481
Sep 21 18:52:16 C02KM0AWFFT4.corp.proofpoint.com softwareupdated[656]: SoftwareUpdate: Invalid or incomplete local product 031-10481
Sep 21 18:52:16 C02KM0AWFFT4.corp.proofpoint.com softwareupdated[656]: Removing local product after found to be incomplete
Sep 21 18:52:16 C02KM0AWFFT4.corp.proofpoint.com softwareupdated[656]: Removed local product for 031-10481 (1)
Sep 21 18:52:16 C02KM0AWFFT4.corp.proofpoint.com softwareupdated[656]: Stopping transaction with ID [0x1]
Sep 21 18:52:16 C02KM0AWFFT4.corp.proofpoint.com softwareupdated[656]: SoftwareUpdate: Removed foreground transaction [0x1]
Sep 21 18:52:16 C02KM0AWFFT4.corp.proofpoint.com storeassetd[995]: SUAppStoreUpdateController: did not start session for 031-10481 (previously installed?)