Signed-off-by: Adam Vandenberg <flangy@gmail.com>

This will be handled by env/superenv, not Python.

Since 9f2782812cbaf2, specifying a version breaks with:

    Error: undefined method `detected_from_url?' for "1.2.2":String

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

I put this require inside the method body, because eager-loading
net/https is slow compared to the rest of Homebrew, and utils.rb is
loaded for each `brew` invocation.

It's probably worth breaking up global.rb a bit, to reduce the amount of
code we are loading unnecessarily, but hopefully also to make inter-file
dependencies a bit more obvious.

Fixes Homebrew/homebrew#21617.

Closes Homebrew/homebrew#21573.

Closes Homebrew/homebrew#21601.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

`brew bottle` already complains and this is a niche case.

References Homebrew/homebrew#21374.

Closes Homebrew/homebrew#21506.
Closes Homebrew/homebrew#21508.

The formula locks used by the installer and commands like link and
unlink are backed by open files and flock(). The open file descriptors
are thus leaked to any subprocesses. This can result in weird behavior
in programs spawned from formula that do not expect to inherit these
descriptors.

Fix this by setting close-on-exec on the lock file descriptors.

Fixes Homebrew/homebrew#21486.

Since xcrun doesn't work on CLT-only systems. Querying HOMEBREW_PREFIX
first before xcrun is much faster for that case.

Fixes Homebrew/homebrew#21417.

Closes Homebrew/homebrew#21390.

Closes Homebrew/homebrew#21385.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

eql? should not depend on the hash value as hash values of uneql objects
can collide, but eql values may only collide for objects that are
actually eql.

Further, python dependencies are uniquely identified by the combination
of the name and imports attributes, so there is no reason to involved
the expensive binary computation for simple equality checks.

Fixes Homebrew/homebrew#20840.