Avoid the need to defensively flatten tags array

Library/Homebrew/dependency_collector.rb

@@ -76,7 +76,7 @@ class DependencyCollector
     elsif (tag = tags.first) && LANGUAGE_MODULES.include?(tag)
       # Next line only for legacy support of `depends_on 'module' => :python`
       # It should be replaced by `depends_on :python => 'module'`
-      return PythonDependency.new("2", spec) if tag == :python
+      return PythonDependency.new("2", Array(spec)) if tag == :python
       LanguageModuleDependency.new(tag, spec)
     else
       Dependency.new(spec, tags)

Library/Homebrew/requirements/python_dependency.rb

@@ -34,7 +34,6 @@ class PythonDependency < Requirement
   end
 
   def initialize(default_version="2.6", tags=[])
-    tags = [tags].flatten
     # Extract the min_version if given. Default to default_version else
     if /(\d+\.)*\d+/ === tags.first.to_s
       @min_version = PythonVersion.new(tags.shift)