[BREAK UPSTREAM] docs: add troubleshooting notes

Author: matbrady

README.md

@@ -17,6 +17,7 @@
   - [Deployment Using Terminus](#deployment-using-terminus)
     - [Test Environment](#test-environment)
     - [Live Environment](#live-environment)
+- [Troubleshooting](/docs/troubleshooting.md)
 
 ## Pantheon Environments
 

docs/troubleshooting.md

@@ -0,0 +1,22 @@
+# Troubleshooting
+
+## Outline
+
+- [Pulling Files and Database from Pantheon Test Environment](pulling-files-and-database-from-pantheon-test-environment)
+
+## Pulling Files and Database from Pantheon Test Environment
+
+Running this command:
+
+```
+lando pull --database=test --files=test --code=none
+```
+
+causes this error:
+
+```
+Notice: Undefined index: X-Pantheon-Styx-Hostname in /var/www/html/vendor/pantheon-systems/terminus/src/Models/Environment.php on line 851
+ [error]  Pantheon headers missing, which is not quite right.
+```
+
+The `test` enviroment has not been created. Dev needs promoted first before the files or database can be pulled from it.