Could you be more specific in the spec file about upstream? There are at least two forks at github. But I guess real upstream development is done here:
https://bitbucket.org/pitrou/pathlib/

> The maintenance repository for this standalone backport module can be found on 
> BitBucket, but activity is expected to be quite low

I would not recommend to download the source tarball from pypi, cause this is guessed to be a redistribution. Better use some URL from bitbucket directly:
https://bitbucket.org/pitrou/pathlib/get/b393963cdf9d.zip (as of 2015-05-01)

1. I did provide upstream url, there's no possible confusion.
You're confusing with pathlib2 which is a fork of pathlib, Antoine Pitrou's version is the reference. We're talking about the backport of python 3.4 standard library module by its maintainer.
2. No, the pristine release is the one in pypi, using bitbucket ugly generated tarball won't cut it.

<rant>
You are right, bitbucket is somehow boring.
https://bitbucket.org/atlassian/stash-archive/issue/7/github-style-download-buttons-tarball-and
</rant>

Maybe try git archive to get a nice tarball of a dedicated commit?
http://git-scm.com/docs/git-archive

Okay, we have this for the official release tags with zip/tar.gz/bz2:
https://bitbucket.org/pitrou/pathlib/downloads

The last option would be inanalogous conjunction with the official policy for github projects. Please notice also the next short chapter about usage of the %{version} macro.
https://fedoraproject.org/wiki/Packaging:SourceURL?rd=Packaging/SourceURL#Github

of course, my comment #3 has to be with a space between in and analogous:
"in analogous conjunction"

Do you plan to provide packages also for EPEL5 and 6? If yes, you have to define the python macros manually.
https://fedoraproject.org/wiki/Packaging:Python#Macros

I am not following why you want to create a tarball from a git while the tarball is on pypi.
Pypi is the canonical place for me to look for releases, tarballs are uploaded their at release time, every one using pip or easy_install is actually relying on it, while github or bitbucket are development places, not releases platform (imho).

Finally, using the pypi tarball will avoid having a potentially different behavior between the RPM and a virtual environment, which I am sure is something developers will appreciate.

APPROVED

Package Review
==============

Legend:
[x] = Pass, [!] = Fail, [-] = Not applicable, [?] = Not evaluated
[ ] = Manual review needed



===== MUST items =====

Generic:
[x]: Package is licensed with an open-source compatible license and meets
     other legal requirements as defined in the legal section of Packaging
     Guidelines.
[x]: License field in the package spec file matches the actual license.
     Note: Checking patched sources after %prep for licenses. Licenses
     found: "Unknown or generated". 4 files have unknown license. Detailed
     output of licensecheck in /home/build/fedora-review/1215150-python-
     pathlib/licensecheck.txt
==> OK. setup.py mentions MIT
[x]: Package contains no bundled libraries without FPC exception.
[x]: Changelog in prescribed format.
[x]: Sources contain only permissible code or content.
[-]: Package contains desktop file if it is a GUI application.
[-]: Development files must be in a -devel package
[x]: Package uses nothing in %doc for runtime.
[x]: Package consistently uses macros (instead of hard-coded directory
     names).
[x]: Package is named according to the Package Naming Guidelines.
[x]: Package does not generate any conflict.
[x]: Package obeys FHS, except libexecdir and /usr/target.
[-]: If the package is a rename of another package, proper Obsoletes and
     Provides are present.
[x]: Requires correct, justified where necessary.
[x]: Spec file is legible and written in American English.
[-]: Package contains systemd file(s) if in need.
[x]: Package is not known to require an ExcludeArch tag.
[x]: Large documentation must go in a -doc subpackage. Large could be size
     (~1MB) or number of files.
     Note: Documentation size is 378880 bytes in 29 files.
[x]: Package complies to the Packaging Guidelines
[x]: Package successfully compiles and builds into binary rpms on at least
     one supported primary architecture.
[x]: Package installs properly.
[x]: Rpmlint is run on all rpms the build produces.
     Note: There are rpmlint messages (see attachment).
[x]: If (and only if) the source package includes the text of the
     license(s) in its own file, then that file, containing the text of the
     license(s) for the package is included in %license.
[x]: Package requires other packages for directories it uses.
[x]: Package must own all directories that it creates.
[x]: Package does not own files or directories owned by other packages.
[x]: All build dependencies are listed in BuildRequires, except for any
     that are listed in the exceptions section of Packaging Guidelines.
[x]: Package uses either %{buildroot} or $RPM_BUILD_ROOT
[x]: Package does not run rm -rf %{buildroot} (or $RPM_BUILD_ROOT) at the
     beginning of %install.
[x]: Macros in Summary, %description expandable at SRPM build time.
[x]: Dist tag is present.
[x]: Package does not contain duplicates in %files.
[x]: Permissions on files are set properly.
[x]: Package use %makeinstall only when make install DESTDIR=... doesn't
     work.
[x]: Package is named using only allowed ASCII characters.
[x]: Package does not use a name that already exists.
[x]: Package is not relocatable.
[x]: Sources used to build the package match the upstream source, as
     provided in the spec URL.
[x]: Spec file name must match the spec package %{name}, in the format
     %{name}.spec.
[x]: File names are valid UTF-8.
[x]: Packages must not store files under /srv, /opt or /usr/local

Python:
[x]: Python eggs must not download any dependencies during the build
     process.
[x]: A package which is used by another package via an egg interface should
     provide egg info.
[x]: Package meets the Packaging Guidelines::Python
[x]: Package contains BR: python2-devel or python3-devel
[x]: Binary eggs must be removed in %prep

===== SHOULD items =====

Generic:
[-]: If the source package does not include license text(s) as a separate
     file from upstream, the packager SHOULD query upstream to include it.
[x]: Final provides and requires are sane (see attachments).
[?]: Package functions as described.
[x]: Latest version is packaged.
[x]: Package does not include license text files separate from upstream.
[-]: Description and summary sections in the package spec file contains
     translations for supported Non-English languages, if available.
[x]: Package should compile and build into binary rpms on all supported
     architectures.
[-]: %check is present and all tests pass.
[x]: Packages should try to preserve timestamps of original installed
     files.
[x]: Packager, Vendor, PreReq, Copyright tags should not be in spec file
[x]: Sources can be downloaded from URI in Source: tag
[x]: Reviewer should test that the package builds in mock.
[x]: Buildroot is not present
[x]: Package has no %clean section with rm -rf %{buildroot} (or
     $RPM_BUILD_ROOT)
[x]: No file requires outside of /etc, /bin, /sbin, /usr/bin, /usr/sbin.
[x]: SourceX is a working URL.
[x]: Spec use %global instead of %define unless justified.

===== EXTRA items =====

Generic:
[x]: Rpmlint is run on all installed packages.
     Note: There are rpmlint messages (see attachment).
[x]: Spec file according to URL is the same as in SRPM.


Rpmlint
-------
Checking: python-pathlib-1.0.1-1.fc23.noarch.rpm
          python-pathlib-1.0.1-1.fc23.src.rpm
python-pathlib.noarch: W: spelling-error Summary(en_US) filesystem -> file system, file-system, systemically
python-pathlib.noarch: W: spelling-error %description -l en_US filesystem -> file system, file-system, systemically
python-pathlib.noarch: W: spelling-error %description -l en_US os -> OS, och, so
python-pathlib.noarch: W: wrong-file-end-of-line-encoding /usr/share/doc/python-pathlib/html/_static/jquery.js
python-pathlib.noarch: W: wrong-file-end-of-line-encoding /usr/share/doc/python-pathlib/html/objects.inv
python-pathlib.noarch: W: file-not-utf8 /usr/share/doc/python-pathlib/html/objects.inv
python-pathlib.src: W: spelling-error Summary(en_US) filesystem -> file system, file-system, systemically
python-pathlib.src: W: spelling-error %description -l en_US filesystem -> file system, file-system, systemically
python-pathlib.src: W: spelling-error %description -l en_US os -> OS, och, so
2 packages and 0 specfiles checked; 0 errors, 9 warnings.




Rpmlint (installed packages)
----------------------------
python-pathlib.noarch: W: spelling-error Summary(en_US) filesystem -> file system, file-system, systemically
python-pathlib.noarch: W: spelling-error %description -l en_US filesystem -> file system, file-system, systemically
python-pathlib.noarch: W: spelling-error %description -l en_US os -> OS, och, so
python-pathlib.noarch: W: wrong-file-end-of-line-encoding /usr/share/doc/python-pathlib/html/_static/jquery.js
python-pathlib.noarch: W: wrong-file-end-of-line-encoding /usr/share/doc/python-pathlib/html/objects.inv
python-pathlib.noarch: W: file-not-utf8 /usr/share/doc/python-pathlib/html/objects.inv
1 packages and 0 specfiles checked; 0 errors, 6 warnings.



Requires
--------
python-pathlib (rpmlib, GLIBC filtered):
    python(abi)



Provides
--------
python-pathlib:
    python-pathlib



Source checksums
----------------
https://pypi.python.org/packages/source/p/pathlib/pathlib-1.0.1.tar.gz :
  CHECKSUM(SHA256) this package     : 6940718dfc3eff4258203ad5021090933e5c04707d5ca8cc9e73c94a7894ea9f
  CHECKSUM(SHA256) upstream package : 6940718dfc3eff4258203ad5021090933e5c04707d5ca8cc9e73c94a7894ea9f


Generated by fedora-review 0.5.3 (bcf15e3) last change: 2015-05-04
Command line :/bin/fedora-review -vv -m fedora-rawhide-x86_64 -b 1215150
Buildroot used: fedora-rawhide-x86_64
Active plugins: Python, Generic, Shell-api
Disabled plugins: Java, C/C++, fonts, SugarActivity, Ocaml, Perl, Haskell, R, PHP, Ruby
Disabled flags: EXARCH, DISTTAG, EPEL5, BATCH, EPEL6

New Package SCM Request
=======================
Package Name: python-pathlib
Short Description: Object-oriented filesystem paths
Upstream URL: https://pathlib.readthedocs.org/
Owners: hguemar apevec
Branches: 
InitialCC:

New Package SCM Request
=======================
Package Name: python-pathlib
Short Description: Object-oriented filesystem paths
Upstream URL: https://pathlib.readthedocs.org/
Owners: hguemar apevec
Branches: epel7 f23
InitialCC:

 Matthias Runge 2015-07-14 09:38:01 CEST
Blocks: 1239832

Why? I fail to see any connection.

Git done (by process-git-requests).