* pytest 3.3.0 has an issue with parametrized null bytes again (#4026)

* add X509_up_ref (#4028)

* changelog and version bump for 2.1.3

* buster is 3.6 now (#4003)

* Fix a few new flake8 issues (#4008)

* Bump version for 2.1.2 release

* rolling has 36 now that it is artful (#3991)

* Latest flake8 has some rules about variable names (#3996)

* Bumped version for release

* attempt to be precise

* backwards incompatible change to UniformResourceIdentifier

During this release cycle we decided to officially deprecate passing
U-labels to our GeneralName constructors. At first we tried changing
this in a purely backwards compatible way but get_values_for_type made
that untenable. This PR modifies URI to accept two types:
U-label strings (which raises a deprecation warning) and A-label strings
(the new preferred type). There is also a constructor for URI
that bypasses validation so we can parse garbage out of certificates
(and round trip it if necessary)

* nonsense empty commit 2.6 and codecov are the worst

* backwards incompatible change to RFC822Name

During this release cycle we decided to officially deprecate passing
U-labels to our GeneralName constructors. At first we tried changing
this in a purely backwards compatible way but get_values_for_type made
that untenable. This PR modifies RFC822Name to accept two types:
U-label strings (which raises a deprecation warning) and A-label strings
(the new preferred type). There is also a constructor for RFC822Name
that bypasses validation so we can parse garbage out of certificates
(and round trip it if necessary)

* whoops

* Backwards incompatible change to DNSName

During this release cycle we decided to officially deprecate passing
U-labels to our GeneralName constructors. At first we tried changing
this in a purely backwards compatible way but get_values_for_type made
that untenable. This PR modifies DNSName to take three different types.
U-label strings (which raises a deprecation warning), A-label strings
(the new preferred type), and bytes (which are assumed to be decodable
to unicode strings). The latter, while supported, is primarily intended
for use by our parser and allows us to return the actual encoded data in
a certificate even if it has not been properly encoded to A-label before
the certificate is created. (Of course, if the certificate contains
invalid utf8 sequences this will still fail, but let's handle one
catastrophic failure at a time).

* coverage

* don't delete that asterisk from a test. it does things.

* no bytes in DNSName. Private constructor for bypassing validation

* test unicode in dnsname (yuck)

* fix docs

* empty commit, you disappoint me codecov

* CI is the worst

* Add support for AES XTS

We drop the non-byte aligned test vectors because according to NIST
http://csrc.nist.gov/groups/STM/cavp/documents/aes/XTSVS.pdf
"An implementation may support a data unit length that is not a
multiple of 8 bits." OpenSSL does not support this, so we can't
use those test vectors.

* fix docs and pep8

* docs fix

* the spellchecker is so frustrating

* add note about AES 192 for XTS (it's not supported)

* docs work

* enforce key length on ECB mode in AES as well (thanks XTS)

* a few more words about why we exclude some test vectors for XTS