env_file parameter results in `no such file or directory` on render

In version docker-app version v0.8.0, build 7eea32b7 on Ubuntu 16.04 when rendering a docker-app with a compose file using 'env_file' always results in

Error: render failed: Action "com.docker.app.render" failed: failed to load Compose file: open /any/env/file: no such file or directory

This occurs regardless if env_file is a parameter or hardcoded, or if the file path is relative or absolute.

Steps to reproduce the issue:

Create a docker app with a docker-compose including 'env_file'
Attempt to render the docker-app

Describe the results you received: no such file or directory

Describe the results you expected: render works

Additional information you deem important (e.g. issue happens only occasionally):

Output of docker version:

$ docker version
Client:
 Version:           18.09.1
 API version:       1.39
 Go version:        go1.10.6
 Git commit:        4c52b90
 Built:             Wed Jan  9 19:35:23 2019
 OS/Arch:           linux/amd64
 Experimental:      false

Server: Docker Engine - Community
 Engine:
  Version:          18.09.1
  API version:      1.39 (minimum version 1.12)
  Go version:       go1.10.6
  Git commit:       4c52b90
  Built:            Wed Jan  9 19:02:44 2019
  OS/Arch:          linux/amd64
  Experimental:     false

Output of docker-app version:

 docker-app version
Version:               v0.8.0
Git commit:            7eea32b7
Built:                 Tue Jun 11 20:53:26 2019
OS/Arch:               linux/amd64
Experimental:          off
Renderers:             none
Invocation Base Image: docker/cnab-app-base:v0.8.0

Output of docker info:

$ docker info
Containers: 954
 Running: 1
 Paused: 0
 Stopped: 953
Images: 2766
Server Version: 18.09.1
Storage Driver: overlay2
 Backing Filesystem: extfs
 Supports d_type: true
 Native Overlay Diff: true
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins:
 Volume: local
 Network: bridge host macvlan null overlay
 Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
Swarm: inactive
Runtimes: runc
Default Runtime: runc
Init Binary: docker-init
containerd version: 9754871865f7fe2f4e74d43e2fc7ccd237edcbce
runc version: 96ec2177ae841256168fcf76954f7177af9446eb
init version: fec3683
Security Options:
 apparmor
 seccomp
  Profile: default
Kernel Version: 4.4.0-142-generic
Operating System: Ubuntu 16.04.5 LTS
OSType: linux
Architecture: x86_64
CPUs: 4
Total Memory: 15.55GiB
Name: mkubilus-x1
ID: ZQ3P:BIEJ:D3AJ:5THN:U23Q:3ULB:CFUJ:EFI3:GUS3:HBLS:ZDEB:3C3U
Docker Root Dir: /home/dockerstuff
Debug Mode (client): false
Debug Mode (server): false
Username: mkubilus
Registry: https://index.docker.io/v1/
Labels:
Experimental: false
Insecure Registries:
 127.0.0.0/8
Live Restore Enabled: false
Product License: Community Engine

WARNING: No swap limit support

Additional environment details (AWS, VirtualBox, physical, etc.):

docker / app

env_file parameter results in `no such file or directory` on render #583