Fix error if local template exists: "no implicit conversion of StringIO into String"

[jesperronn]

I ran into this problem, when I had a template in my project config/deploy/templates/postgresql.yml.erb.

The code further up the call stack, will run StringIO.new() which results in a failure:

capistrano-postgresql/lib/capistrano/tasks/postgresql.rake

Lines 126 to 128 in 77ae455

	upload!(
	StringIO.new(pg_template),
	archetype_database_yml_file

So in the case where pg_template() method returns a StringIO we see this error:

~/.rvm/gems/ruby-3.1.2/gems/sshkit-1.21.3/lib/sshkit/runners/parallel.rb:15:in `rescue in block (2 levels) in execute': 
    Exception while executing on host xxxx: no implicit conversion of StringIO into String (SSHKit::Runner::ExecuteError)
	from ~/.rvm/gems/ruby-3.1.2/gems/sshkit-1.21.3/lib/sshkit/runners/parallel.rb:11:in `block (2 levels) in execute'
~/.rvm/gems/ruby-3.1.2/gems/capistrano-postgresql-6.2.0/lib/capistrano/tasks/postgresql.rake:127:in `initialize': no implicit conversion of StringIO into String (TypeError)
	from ~/.rvm/gems/ruby-3.1.2/gems/capistrano-postgresql-6.2.0/lib/capistrano/tasks/postgresql.rake:127:in `new'
	from ~/.rvm/gems/ruby-3.1.2/gems/capistrano-postgresql-6.2.0/lib/capistrano/tasks/postgresql.rake:127:in `block (3 levels) in <top (required)>'
	from ~/.rvm/gems/ruby-3.1.2/gems/sshkit-1.21.3/lib/sshkit/backends/abstract.rb:31:in `instance_exec'
	from ~/.rvm/gems/ruby-3.1.2/gems/sshkit-1.21.3/lib/sshkit/backends/abstract.rb:31:in `run'
	from ~/.rvm/gems/ruby-3.1.2/gems/sshkit-1.21.3/lib/sshkit/runners/parallel.rb:12:in `block (2 levels) in execute'
(Backtrace restricted to imported tasks)
cap aborted!
SSHKit::Runner::ExecuteError: Exception while executing on host xxxx: no implicit conversion of StringIO into String


Caused by:
TypeError: no implicit conversion of StringIO into String

Tasks: TOP => postgresql:generate_database_yml_archetype

The PR here fixes the bug. I saw no tests in the library, and also my rubocop noted a lot of issues in the file already.

With the lack of tests and lack of linting, please review carefully.

[jesperronn]

If others run into this issue, my workaround was to remove the file config/deploy/templates/postgresql.yml.erb.