Pass env vars to docker (serverless#271)

* Add environment variables to docker run cmd

* Pass env vars to docker

Based on serverless#231 & closes serverless#267

* format

* fix docs

* Update README.md

Author: dschep

README.md

@@ -72,6 +72,15 @@ It is important that the host of your private repositories has already been adde
 `$HOME/.ssh/known_hosts` file, as the install process will fail otherwise due to host authenticity
 failure.
 
+You can also pass environment variables to docker by specifying them in `dockerEnv`
+option:
+```yaml
+custom:
+  pythonRequirements:
+    dockerEnv:
+      - https_proxy
+```
+
 [:checkered_flag: Windows notes](#checkered_flag-windows-dockerizepip-notes)
 
 ## Pipenv support :sparkles::cake::sparkles:

index.js

@@ -42,6 +42,7 @@ class ServerlessPythonRequirements {
         dockerSsh: false,
         dockerImage: null,
         dockerFile: null,
+        dockerEnv: false,
         useStaticCache: false,
         useDownloadCache: false,
         cacheLocation: false,

lib/pip.js

@@ -196,6 +196,13 @@ function installRequirements(targetFolder, serverless, options) {
       pipCmd.push('--cache-dir', quote_single(dockerDownloadCacheDir));
     }
 
+    if (options.dockerEnv) {
+      // Add environment variables to docker run cmd
+      options.dockerEnv.forEach(function(item) {
+        cmdOptions.push('-e', item);
+      });
+    }
+
     if (process.platform === 'linux') {
       // Use same user so requirements folder is not root and so --cache-dir works
       var commands = [];