Ran into this when I was setting up a Capistrano. I had setup my Github keys under my admin account, and not the account I had setup for Capistrano to use.

Make sure your keys are setup for the right account.

A

You probably forgot to make something public in your class:

class A {
  A() {};
};

class A {
public:
  A() {};
};

g++ ‘s version of the error message is a bit more clear:

error: A::A() is private