Trac #30446: Update pynac to 0.7.27 to fix wrong result on symbolic exponentiation

{{{
sage: n((24*sqrt(3))^(100/50))
3.80392047155301e5927962146
sage: n((24*sqrt(3))^(2))
1728.00000000000
}}}
Clearly, both should be the same, namely the second.

This was on SageMath 9.1 on openSUSE Leap 15.2 (64bit) (reported by a
colleague to me).

I've tried to reproduce, but my SageMath, as well as on Cocalc crashes.
The error message on my machine was
{{{
Traceback (most recent call last):
  File "<string>", line 25, in <module>
ModuleNotFoundError: No module named 'Cython'
Error while executing Python code.
Saved trace to /home/dakrenn/.sage/crash_logs/crash_lqkqgydq.log
------------------------------------------------------------------------
Unhandled SIGABRT: An abort() occurred.
This probably occurred because a *compiled* module has a bug
in it and is not properly wrapped with sig_on(), sig_off().
Python will now terminate.
------------------------------------------------------------------------
Aborted (core dumped)
}}}
However, my SageMath seems to be fine otherwise, `make ptestlong`
passes.
Same on current 9.2.beta9.

URL: https://trac.sagemath.org/30446
Reported by: dkrenn
Ticket author(s): Ben Livingston, Dima Pasechnik
Reviewer(s): Dima Pasechnik, Matthias Koeppe

Author: Release Manager

build/pkgs/pynac/SPKG.rst

@@ -16,6 +16,7 @@ GPL V2+
 Upstream Contact
 ----------------
 
+-  https://github.com/pynac/pynac
 -  http://pynac.org
 -  Burcin Erocal - burcin spam.erocal.org
 -  William Stein - wstein spam.gmail.com
@@ -25,13 +26,3 @@ Dependencies
 ------------
 
 Python
-
-
-Special Update/Build Instructions
----------------------------------
-
-If build fails trying to run autoheader, run
-
-   autoreconf -i --force
-
-in the src directory.

build/pkgs/pynac/checksums.ini

@@ -1,5 +1,5 @@
 tarball=pynac-VERSION.tar.bz2
-sha1=4913173e8bbb3d79bb4ee1faf631b154c9b8ef8c
-md5=b38234ffedc018e7f31217dcc2879035
-cksum=881228674
-upstream_url=https://github.com/mkoeppe/pynac/releases/download/pynac-VERSION/pynac-VERSION.tar.bz2
+sha1=948ab5d8f81abd87669cd0b48916cfeffd772868
+md5=22275a875cd14bf55689987fb6bb846f
+cksum=3697405663
+upstream_url=https://github.com/pynac/pynac/releases/download/pynac-VERSION/pynac-VERSION.tar.bz2

build/pkgs/pynac/package-version.txt

@@ -1 +1 @@
-0.7.26.sage-2020-04-03.p0
+0.7.27.p0

build/pkgs/pynac/patches/py_ssize_t_clean.patch

@@ -1231,6 +1231,13 @@ cdef class Expression(CommutativeRingElement):
 
             sage: latex(1+x^(2/3)+x^(-2/3))
             x^{\frac{2}{3}} + \frac{1}{x^{\frac{2}{3}}} + 1
+
+        Check that pynac understands rational powers (:trac:`30446`)::
+
+            sage: QQ((24*sqrt(3))^(100/50))==1728
+            True
+            sage: float((24*sqrt(3))^(100/51))
+            1493.0092154...
         """
         return self._parent._latex_element_(self)