1 files changed, 11 insertions, 0 deletions
diff --git a/Library/Homebrew/exceptions.rb b/Library/Homebrew/exceptions.rb
index e01a60c75..1b2b24691 100644
--- a/Library/Homebrew/exceptions.rb
+++ b/Library/Homebrew/exceptions.rb
@@ -294,6 +294,17 @@ class FormulaConflictError < RuntimeError
   end
 end
 
+class FormulaAmbiguousPythonError < RuntimeError
+  def initialize(formula)
+    super <<-EOS.undent
+      The version of python to use with the virtualenv in the `#{formula.full_name}` formula
+      cannot be guessed automatically. If the simultaneous use of python and python3
+      is intentional, please add `:using => "python"` or `:using => "python3"` to
+      `virtualenv_install_with_resources` to resolve the ambiguity manually.
+    EOS
+  end
+end
+
 class BuildError < RuntimeError
   attr_reader :formula, :env