[fix] Adapt tests to extra-paths changes

Now that extra-paths is sys.path by default instead of the legacy
value of the specific paths of zc.buildout and its dependencies,
some tests fail because some eggs in sys.path that were previously
not in extra-paths were instead found on sys.path by package index's
search_path and subsequently installed in ./eggs, whereas they are
now directly seen as already installed at their original location.

doc/getting-started.rst

@@ -113,6 +113,7 @@ update our Buildout configuration to add a ``bobo`` part:
 
   [buildout]
   parts = bobo
+  extra-paths = legacy
 
   [bobo]
   recipe = zc.recipe.egg
@@ -426,6 +427,7 @@ where you list them, as in:
    >>> prefix = """
    ... [buildout]
    ... parts = bobo
+   ... extra-paths = legacy
    ... """
    >>> with open('buildout.cfg', 'w') as f:
    ...     _ = f.write(prefix)
@@ -458,6 +460,7 @@ The more common way to pin a version is using a ``versions`` section:
 
   [buildout]
   parts = bobo server
+  extra-paths = legacy
 
   [bobo]
   recipe = zc.recipe.egg
@@ -489,6 +492,7 @@ version requirements in their own file:
   [buildout]
   extends = versions.cfg
   parts = bobo server
+  extra-paths = legacy
 
   [bobo]
   recipe = zc.recipe.egg

doc/topics/optimizing.rst

@@ -21,6 +21,7 @@ Buildout work better:
     >>> write("""\
     ... [buildout]
     ... parts = bobo
+    ... extra-paths = legacy
     ... [bobo]
     ... recipe=zc.recipe.egg
     ... eggs=bobo

doc/topics/variables-extending-and-substitutions.rst

@@ -248,6 +248,7 @@ is typically used to set up a shared egg or cache directory, as in:
     >>> write("""\
     ... [buildout]
     ... parts = bobo
+    ... extra-paths = legacy
     ... [bobo]
     ... recipe=zc.recipe.egg
     ... eggs=bobo