Extension fails to install on Debian 8 (20170315)

Extension fails to install on `credativ:debian:8:8.0.201703150` image.

My guess is that `python` has no mapping in this version of the image. For example:
```
$ ./customscript.py -install
/usr/bin/env: python: No such file or directory
$ echo $?
127
```

WALA logs:
```
2017/03/25 02:07:31.231113 INFO Activate resource disk
2017/03/25 02:07:31.280661 INFO Examining partition table
2017/03/25 02:07:31.301111 INFO GPT not detected, determining filesystem
2017/03/25 02:07:31.321489 INFO The partition is formatted with ntfs, updating partition type to 83
2017/03/25 02:07:31.405615 INFO Format partition [mkfs.ext4 /dev/sdb1 -F]
2017/03/25 02:07:49.007700 INFO Mount resource disk [mount /dev/sdb1 /mnt/resource]
2017/03/25 02:07:49.278264 INFO Resource disk /dev/sdb is mounted at /mnt/resource with ext4
2017/03/25 02:07:56.929515 INFO Running provisioning handler
2017/03/25 02:07:56.950533 INFO Copying ovf-env.xml
2017/03/25 02:07:57.106432 INFO Successfully mounted dvd
2017/03/25 02:07:57.619762 INFO Detect protocol by file
2017/03/25 02:07:57.635226 INFO Clean protocol
2017/03/25 02:07:57.647254 INFO WireServer endpoint is not found. Rerun dhcp handler
2017/03/25 02:07:57.667693 INFO test for route to 168.63.129.16
2017/03/25 02:07:57.687357 INFO route to 168.63.129.16 exists
2017/03/25 02:07:57.708723 INFO Wire server endpoint:168.63.129.16
2017/03/25 02:07:57.747093 INFO Fabric preferred wire protocol version:2015-04-05
2017/03/25 02:07:57.765158 INFO Wire protocol version:2012-11-30
2017/03/25 02:07:57.777521 WARNING Server prefered version:2015-04-05
2017/03/25 02:08:02.793252 INFO Starting provisioning
2017/03/25 02:08:02.800801 INFO Handle ovf-env.xml.
2017/03/25 02:08:02.808543 INFO Set host name.
2017/03/25 02:08:02.838545 INFO Publish host name.
2017/03/25 02:08:02.845988 INFO examine /proc/net/route for primary interface
2017/03/25 02:08:02.855748 INFO primary interface is [eth0]
2017/03/25 02:08:02.863957 INFO interface [b'lo'] has flags [73], is loopback [True]
2017/03/25 02:08:02.874530 INFO interface [b'lo'] skipped
2017/03/25 02:08:02.882847 INFO interface [b'eth0'] has flags [4163], is loopback [False]
2017/03/25 02:08:02.894697 INFO interface [b'eth0'] selected
2017/03/25 02:08:09.500438 INFO Create user account if not exists
2017/03/25 02:08:10.393279 INFO Set user password.
2017/03/25 02:08:10.624369 INFO Configure sudoer
2017/03/25 02:08:10.640190 INFO Configure sshd
2017/03/25 02:08:10.656313 INFO Enabled SSH password-based authentication methods.
2017/03/25 02:08:10.676208 INFO Configured SSH client probing to keep connections alive.
2017/03/25 02:08:11.368991 INFO Event: name=WALA, op=Provision, message=Provision succeed
2017/03/25 02:08:13.830117 INFO Provisioning complete
2017/03/25 02:08:14.766041 INFO Azure Linux Agent Version:2.2.2
2017/03/25 02:08:14.780388 INFO OS: debian 8.7
2017/03/25 02:08:14.793948 INFO Python: 3.4.2
2017/03/25 02:08:14.804170 INFO Run daemon
2017/03/25 02:08:14.818943 INFO No RDMA handler exists for distro='debian' version='8.7'
2017/03/25 02:08:14.835688 INFO Activate resource disk
2017/03/25 02:08:14.864129 INFO Resource disk [/dev/sdb1] is already mounted [/mnt/resource]
2017/03/25 02:08:14.881248 INFO Clean protocol
2017/03/25 02:08:14.891764 INFO Provisioning already completed, skipping.
2017/03/25 02:08:14.907497 INFO RDMA capabilities are not enabled, skipping
2017/03/25 02:08:14.920904 INFO Installed Agent WALinuxAgent-2.2.2 is the most current agent
2017/03/25 02:08:14.976151 INFO Agent WALinuxAgent-2.2.2 launched with command 'python3 -u /usr/sbin/waagent -run-exthandlers'
2017/03/25 02:08:15.413238 INFO Agent WALinuxAgent-2.2.2 is running as the goal state agent
2017/03/25 02:08:15.441195 INFO Detect protocol endpoints
2017/03/25 02:08:15.461588 INFO Clean protocol
2017/03/25 02:08:15.468425 INFO WireServer endpoint is not found. Rerun dhcp handler
2017/03/25 02:08:15.483497 INFO test for route to 168.63.129.16
2017/03/25 02:08:15.500139 INFO route to 168.63.129.16 exists
2017/03/25 02:08:15.512056 INFO Wire server endpoint:168.63.129.16
2017/03/25 02:08:15.557818 INFO Fabric preferred wire protocol version:2015-04-05
2017/03/25 02:08:15.571830 INFO Wire protocol version:2012-11-30
2017/03/25 02:08:15.589275 WARNING Server prefered version:2015-04-05
2017/03/25 02:08:20.687258 INFO Event: name=WALinuxAgent-2.2.2, op=HeartBeat, message=
2017/03/25 02:08:20.703033 INFO Start env monitor service.
2017/03/25 02:08:20.713714 INFO Configure routes
2017/03/25 02:08:20.726253 INFO Gateway:None
2017/03/25 02:08:20.731054 INFO Routes:None
2017/03/25 02:08:20.854438 INFO WALinuxAgent-2.2.2 running as process 495
2017/03/25 02:08:20.862291 INFO Set block dev timeout: sda with timeout: 300
2017/03/25 02:08:20.873628 INFO Checking for agent family Prod updates
2017/03/25 02:08:20.884557 INFO Set block dev timeout: sdb with timeout: 300
2017/03/25 02:08:20.895775 INFO Wire server endpoint:168.63.129.16
2017/03/25 02:08:20.976879 INFO Instantiating Agent WALinuxAgent-2.2.1 from package
2017/03/25 02:08:20.994225 INFO Agent WALinuxAgent-2.2.1 error state: Last Failure: 0.0, Total Failures: 0, Fatal: False
2017/03/25 02:08:21.017209 INFO Ensuring Agent WALinuxAgent-2.2.1 is downloaded
2017/03/25 02:08:21.096648 INFO Agent WALinuxAgent-2.2.1 downloaded from https://brdfepirv2by3prdstr04.blob.core.windows.net/7d89d439b79f4452950452399add2c90/Microsoft.OSTCLinuxAgent__Prod__2.2.1
2017/03/25 02:08:21.158679 INFO Agent WALinuxAgent-2.2.1 unpacked successfully to /var/lib/waagent/WALinuxAgent-2.2.1
2017/03/25 02:08:21.192721 INFO Agent WALinuxAgent-2.2.1 loaded manifest from /var/lib/waagent/WALinuxAgent-2.2.1/HandlerManifest.json
2017/03/25 02:08:21.213111 INFO Agent WALinuxAgent-2.2.1 error state: Last Failure: 0.0, Total Failures: 0, Fatal: False
2017/03/25 02:08:21.245519 INFO Agent WALinuxAgent-2.2.1 downloaded successfully
2017/03/25 02:08:21.255739 INFO Event: name=WALinuxAgent, op=Install, message=Agent WALinuxAgent-2.2.1 downloaded successfully
2017/03/25 02:08:21.275410 INFO Instantiating Agent WALinuxAgent-2.2.2 from package
2017/03/25 02:08:21.302110 INFO Agent WALinuxAgent-2.2.2 error state: Last Failure: 0.0, Total Failures: 0, Fatal: False
2017/03/25 02:08:21.316286 INFO Ensuring Agent WALinuxAgent-2.2.2 is downloaded
2017/03/25 02:08:21.422029 INFO Agent WALinuxAgent-2.2.2 downloaded from https://brdfepirv2by3prdstr04.blob.core.windows.net/7d89d439b79f4452950452399add2c90/Microsoft.OSTCLinuxAgent__Prod__2.2.2
2017/03/25 02:08:21.472241 INFO Agent WALinuxAgent-2.2.2 unpacked successfully to /var/lib/waagent/WALinuxAgent-2.2.2
2017/03/25 02:08:21.490276 INFO Agent WALinuxAgent-2.2.2 loaded manifest from /var/lib/waagent/WALinuxAgent-2.2.2/HandlerManifest.json
2017/03/25 02:08:21.529712 INFO Agent WALinuxAgent-2.2.2 error state: Last Failure: 0.0, Total Failures: 0, Fatal: False
2017/03/25 02:08:21.550549 INFO Agent WALinuxAgent-2.2.2 downloaded successfully
2017/03/25 02:08:21.575573 INFO Event: name=WALinuxAgent, op=Install, message=Agent WALinuxAgent-2.2.2 downloaded successfully
2017/03/25 02:08:21.593339 INFO Instantiating Agent WALinuxAgent-2.2.5 from package
2017/03/25 02:08:21.622768 INFO Agent WALinuxAgent-2.2.5 error state: Last Failure: 0.0, Total Failures: 0, Fatal: False
2017/03/25 02:08:21.636951 INFO Ensuring Agent WALinuxAgent-2.2.5 is downloaded
2017/03/25 02:08:21.769485 INFO Agent WALinuxAgent-2.2.5 downloaded from https://brdfepirv2by3prdstr04.blob.core.windows.net/7d89d439b79f4452950452399add2c90/Microsoft.OSTCLinuxAgent__Prod__2.2.5
2017/03/25 02:08:21.842944 INFO Agent WALinuxAgent-2.2.5 unpacked successfully to /var/lib/waagent/WALinuxAgent-2.2.5
2017/03/25 02:08:21.860068 INFO Agent WALinuxAgent-2.2.5 loaded manifest from /var/lib/waagent/WALinuxAgent-2.2.5/HandlerManifest.json
2017/03/25 02:08:21.881205 INFO Agent WALinuxAgent-2.2.5 error state: Last Failure: 0.0, Total Failures: 0, Fatal: False
2017/03/25 02:08:21.910867 INFO Agent WALinuxAgent-2.2.5 downloaded successfully
2017/03/25 02:08:21.920051 INFO Event: name=WALinuxAgent, op=Install, message=Agent WALinuxAgent-2.2.5 downloaded successfully
2017/03/25 02:08:21.938078 INFO Instantiating Agent WALinuxAgent-2.2.6 from package
2017/03/25 02:08:21.966859 INFO Agent WALinuxAgent-2.2.6 error state: Last Failure: 0.0, Total Failures: 0, Fatal: False
2017/03/25 02:08:21.980467 INFO Ensuring Agent WALinuxAgent-2.2.6 is downloaded
2017/03/25 02:08:22.091122 INFO Agent WALinuxAgent-2.2.6 downloaded from https://brdfepirv2by3prdstr04.blob.core.windows.net/7d89d439b79f4452950452399add2c90/Microsoft.OSTCLinuxAgent__Prod__2.2.6
2017/03/25 02:08:22.144034 INFO Agent WALinuxAgent-2.2.6 unpacked successfully to /var/lib/waagent/WALinuxAgent-2.2.6
2017/03/25 02:08:22.166077 INFO Agent WALinuxAgent-2.2.6 loaded manifest from /var/lib/waagent/WALinuxAgent-2.2.6/HandlerManifest.json
2017/03/25 02:08:22.191784 INFO Agent WALinuxAgent-2.2.6 error state: Last Failure: 0.0, Total Failures: 0, Fatal: False
2017/03/25 02:08:22.209643 INFO Agent WALinuxAgent-2.2.6 downloaded successfully
2017/03/25 02:08:22.245929 INFO Event: name=WALinuxAgent, op=Install, message=Agent WALinuxAgent-2.2.6 downloaded successfully
2017/03/25 02:08:22.262234 INFO Agent WALinuxAgent-2.2.2 discovered WALinuxAgent-2.2.6 as an update and will exit
2017/03/25 02:09:15.083839 INFO Agent WALinuxAgent-2.2.2 launched with command 'python3 -u /usr/sbin/waagent -run-exthandlers' is successfully running
2017/03/25 02:09:15.101182 INFO Event: name=WALinuxAgent, op=Enable, message=Agent WALinuxAgent-2.2.2 launched with command 'python3 -u /usr/sbin/waagent -run-exthandlers' is successfully running
2017/03/25 02:09:15.124278 INFO Instantiating Agent WALinuxAgent-2.2.1 from disk
2017/03/25 02:09:15.134776 INFO Agent WALinuxAgent-2.2.1 error state: Last Failure: 0.0, Total Failures: 0, Fatal: False
2017/03/25 02:09:15.149031 INFO Ensuring Agent WALinuxAgent-2.2.1 is downloaded
2017/03/25 02:09:15.158847 INFO Agent WALinuxAgent-2.2.1 was previously downloaded - skipping download
2017/03/25 02:09:15.171622 INFO Agent WALinuxAgent-2.2.1 loaded manifest from /var/lib/waagent/WALinuxAgent-2.2.1/HandlerManifest.json
2017/03/25 02:09:15.188173 INFO Instantiating Agent WALinuxAgent-2.2.2 from disk
2017/03/25 02:09:15.198048 INFO Agent WALinuxAgent-2.2.2 error state: Last Failure: 0.0, Total Failures: 0, Fatal: False
2017/03/25 02:09:15.212044 INFO Ensuring Agent WALinuxAgent-2.2.2 is downloaded
2017/03/25 02:09:15.221069 INFO Agent WALinuxAgent-2.2.2 was previously downloaded - skipping download
2017/03/25 02:09:15.232327 INFO Agent WALinuxAgent-2.2.2 loaded manifest from /var/lib/waagent/WALinuxAgent-2.2.2/HandlerManifest.json
2017/03/25 02:09:15.248563 INFO Instantiating Agent WALinuxAgent-2.2.5 from disk
2017/03/25 02:09:15.258828 INFO Agent WALinuxAgent-2.2.5 error state: Last Failure: 0.0, Total Failures: 0, Fatal: False
2017/03/25 02:09:15.272923 INFO Ensuring Agent WALinuxAgent-2.2.5 is downloaded
2017/03/25 02:09:15.282095 INFO Agent WALinuxAgent-2.2.5 was previously downloaded - skipping download
2017/03/25 02:09:15.293663 INFO Agent WALinuxAgent-2.2.5 loaded manifest from /var/lib/waagent/WALinuxAgent-2.2.5/HandlerManifest.json
2017/03/25 02:09:15.308546 INFO Instantiating Agent WALinuxAgent-2.2.6 from disk
2017/03/25 02:09:15.317782 INFO Agent WALinuxAgent-2.2.6 error state: Last Failure: 0.0, Total Failures: 0, Fatal: False
2017/03/25 02:09:15.330913 INFO Ensuring Agent WALinuxAgent-2.2.6 is downloaded
2017/03/25 02:09:15.340152 INFO Agent WALinuxAgent-2.2.6 was previously downloaded - skipping download
2017/03/25 02:09:15.351675 INFO Agent WALinuxAgent-2.2.6 loaded manifest from /var/lib/waagent/WALinuxAgent-2.2.6/HandlerManifest.json
2017/03/25 02:09:15.367358 INFO Determined Agent WALinuxAgent-2.2.6 to be the latest agent
2017/03/25 02:09:15.379825 INFO Agent WALinuxAgent-2.2.6 launched with command 'python3 -u bin/WALinuxAgent-2.2.6-py2.7.egg -run-exthandlers'
2017/03/25 02:09:16.080018 INFO Agent WALinuxAgent-2.2.6 is running as the goal state agent
2017/03/25 02:09:16.124716 INFO Wire server endpoint:168.63.129.16
2017/03/25 02:09:16.154061 INFO Start env monitor service.
2017/03/25 02:09:16.152755 INFO Event: name=WALinuxAgent-2.2.6, op=HeartBeat, message=
2017/03/25 02:09:16.165720 INFO Configure routes
2017/03/25 02:09:16.195709 INFO Gateway:None
2017/03/25 02:09:16.203258 INFO Routes:None
2017/03/25 02:09:16.215101 WARNING Hostname record does not exist, creating [/var/lib/waagent/published_hostname] with hostname [batchnode-0]
2017/03/25 02:09:16.258920 WARNING Dhcp client is not running.
2017/03/25 02:09:16.268117 INFO WALinuxAgent-2.2.6 running as process 513
2017/03/25 02:09:16.294145 INFO Checking for agent family Prod updates
2017/03/25 02:09:16.309180 INFO Wire server endpoint:168.63.129.16
2017/03/25 02:09:16.404672 INFO Instantiating Agent WALinuxAgent-2.2.1 from package
2017/03/25 02:09:16.418301 INFO Agent WALinuxAgent-2.2.1 error state: Last Failure: 0.0, Total Failures: 0, Fatal: False
2017/03/25 02:09:16.441203 INFO Ensuring Agent WALinuxAgent-2.2.1 is downloaded
2017/03/25 02:09:16.457387 INFO Agent WALinuxAgent-2.2.1 was previously downloaded - skipping download
2017/03/25 02:09:16.478500 INFO Agent WALinuxAgent-2.2.1 loaded manifest from /var/lib/waagent/WALinuxAgent-2.2.1/HandlerManifest.json
2017/03/25 02:09:16.499440 INFO Instantiating Agent WALinuxAgent-2.2.2 from package
2017/03/25 02:09:16.523125 INFO Agent WALinuxAgent-2.2.2 error state: Last Failure: 0.0, Total Failures: 0, Fatal: False
2017/03/25 02:09:16.541782 INFO Ensuring Agent WALinuxAgent-2.2.2 is downloaded
2017/03/25 02:09:16.564603 INFO Agent WALinuxAgent-2.2.2 was previously downloaded - skipping download
2017/03/25 02:09:16.603466 INFO Agent WALinuxAgent-2.2.2 loaded manifest from /var/lib/waagent/WALinuxAgent-2.2.2/HandlerManifest.json
2017/03/25 02:09:16.634749 INFO Instantiating Agent WALinuxAgent-2.2.5 from package
2017/03/25 02:09:16.660447 INFO Agent WALinuxAgent-2.2.5 error state: Last Failure: 0.0, Total Failures: 0, Fatal: False
2017/03/25 02:09:16.674802 INFO Ensuring Agent WALinuxAgent-2.2.5 is downloaded
2017/03/25 02:09:16.700667 INFO Agent WALinuxAgent-2.2.5 was previously downloaded - skipping download
2017/03/25 02:09:16.717317 INFO Agent WALinuxAgent-2.2.5 loaded manifest from /var/lib/waagent/WALinuxAgent-2.2.5/HandlerManifest.json
2017/03/25 02:09:16.748166 INFO Instantiating Agent WALinuxAgent-2.2.6 from package
2017/03/25 02:09:16.757824 INFO Agent WALinuxAgent-2.2.6 error state: Last Failure: 0.0, Total Failures: 0, Fatal: False
2017/03/25 02:09:16.777167 INFO Ensuring Agent WALinuxAgent-2.2.6 is downloaded
2017/03/25 02:09:16.797375 INFO Agent WALinuxAgent-2.2.6 was previously downloaded - skipping download
2017/03/25 02:09:16.813744 INFO Agent WALinuxAgent-2.2.6 loaded manifest from /var/lib/waagent/WALinuxAgent-2.2.6/HandlerManifest.json
2017/03/25 02:09:16.844312 INFO Wire server endpoint:168.63.129.16
2017/03/25 02:09:16.959683 INFO [Microsoft.OSTCExtensions.CustomScriptForLinux-1.5.2.1] Expected handler state: enabled
2017/03/25 02:09:16.987932 INFO [Microsoft.OSTCExtensions.CustomScriptForLinux-1.5.2.1] Current handler state is: NotInstalled
2017/03/25 02:09:17.002335 INFO [Microsoft.OSTCExtensions.CustomScriptForLinux-1.5.2.1] Download extension package
2017/03/25 02:09:17.079047 INFO [Microsoft.OSTCExtensions.CustomScriptForLinux-1.5.2.1] Unpack extension package
2017/03/25 02:09:17.153192 INFO Event: name=Microsoft.OSTCExtensions.CustomScriptForLinux, op=Download, message=Download succeeded
2017/03/25 02:09:17.174601 INFO [Microsoft.OSTCExtensions.CustomScriptForLinux-1.5.2.1] Initialize extension directory
2017/03/25 02:09:17.199354 INFO [Microsoft.OSTCExtensions.CustomScriptForLinux-1.5.2.1] Update settings file: 0.settings
2017/03/25 02:09:17.218290 INFO [Microsoft.OSTCExtensions.CustomScriptForLinux-1.5.2.1] Install extension.
2017/03/25 02:09:17.247488 INFO [Microsoft.OSTCExtensions.CustomScriptForLinux-1.5.2.1] Launch command:customscript.py -install
2017/03/25 02:09:18.272756 ERROR Event: name=Microsoft.OSTCExtensions.CustomScriptForLinux, op=Install, message=(000003)Non-zero exit code: 127, customscript.py -install
2017/03/25 02:09:18.369199 INFO Event: name=WALinuxAgent, op=HealthCheck, message=Blob type match [BlockBlob]
2017/03/25 02:24:16.134562 INFO Agent WALinuxAgent-2.2.6 launched with command 'python3 -u bin/WALinuxAgent-2.2.6-py2.7.egg -run-exthandlers' is successfully running
2017/03/25 02:24:16.146524 INFO Event: name=WALinuxAgent, op=Enable, message=Agent WALinuxAgent-2.2.6 launched with command 'python3 -u bin/WALinuxAgent-2.2.6-py2.7.egg -run-exthandlers' is successfully running
2017/03/25 02:24:16.146524 INFO Event: name=WALinuxAgent, op=Enable, message=Agent WALinuxAgent-2.2.6 launched with command 'python3 -u bin/WALinuxAgent-2.2.6-py2.7.egg -run-exthandlers' is successfully running
2017/03/25 02:39:18.977621 INFO Event: name=WALinuxAgent-2.2.6, op=HeartBeat, message=
```

`config/HandlerState`:
```
NotInstalled
```

`config/HandlerStatus`:
```json
{"version": "1.5.2.1", "name": "Microsoft.OSTCExtensions.CustomScriptForLinux", "code": -1, "extensions": [], "status": "NotReady", "message": "(000003)Non-zero exit code: 127, customscript.py -install"}
```

`status`:
directory is empty