Failure sending request can occur during a VM provisioning once in a while

[yashirot]

Sometimes Failure sending request occurs as mentioned in PR #53
But excluding some characters from using in a Windows password, like PR #53 did, is apparently not a radical solution.

From PR #53:

│ Error: compute.VirtualMachinesClient#CreateOrUpdate: Failure sending request: StatusCode=400 -- Original Error: Code="InvalidParameter" Message="The value of parameter windowsConfiguration.additionalUnattendContent.content is invalid." Target="windowsConfiguration.additionalUnattendContent.content"
│
│   with module.firefox_verify_env.azurerm_virtual_machine.firefoxverify_vm,
│   on ../../modules/main.tf line 54, in resource "azurerm_virtual_machine" "firefoxverify_vm":
│   54: resource "azurerm_virtual_machine" "firefoxverify_vm" {

Known workaround:

1. On portal.azure.com, purge all the resources in the resource group to be deploying
2. Start make--including terraform apply etc.-- once again

Objectives:
To make it clear

1. how it occurs
2. how to solve it