I just found a couple of nasty errors that didn't allowed me to install trezor-agent via pip. A couple of examples are:

    Failed building wheel for hidapi
      /usr/bin/ld: cannot find -ludev
      collect2: error: ld returned 1 exit status
      error: command 'x86_64-linux-gnu-gcc' failed with exit status 1
      hidapi/libusb/hid.c:47:20: fatal error: libusb.h: No such file or directory
      compilation terminated.
      error: command 'x86_64-linux-gnu-gcc' failed with exit status 1

The problem resides on the build of hidapi. To solve it, you must install the requirements present in their github page

    Prerequisites:
    ---------------
    Linux:
    -------
    On Linux, you will need to install development packages for libudev,
    libusb and optionally Fox-toolkit (for the test GUI). On
    Debian/Ubuntu systems these can be installed by running:
        sudo apt-get install libudev-dev libusb-1.0-0-dev libfox-1.6-dev

    If you downloaded the source directly from the git repository (using
    git clone), you'll need Autotools:
        sudo apt-get install autotools-dev autoconf automake libtool

    FreeBSD:
    ---------
    On FreeBSD you will need to install GNU make, libiconv, and
    optionally Fox-Toolkit (for the test GUI). This is done by running
    the following:
        pkg_add -r gmake libiconv fox16

    If you downloaded the source directly from the git repository (using
    git clone), you'll need Autotools:
        pkg_add -r autotools

    Mac:
    -----
    On Mac, you will need to install Fox-Toolkit if you wish to build
    the Test GUI. There are two ways to do this, and each has a slight
    complication. Which method you use depends on your use case.

    If you wish to build the Test GUI just for your own testing on your
    own computer, then the easiest method is to install Fox-Toolkit
    using ports:
        sudo port install fox

    If you wish to build the TestGUI app bundle to redistribute to
    others, you will need to install Fox-toolkit from source.  This is
    because the version of fox that gets installed using ports uses the
    ports X11 libraries which are not compatible with the Apple X11
    libraries.  If you install Fox with ports and then try to distribute
    your built app bundle, it will simply fail to run on other systems.
    To install Fox-Toolkit manually, download the source package from
    http://www.fox-toolkit.org, extract it, and run the following from
    within the extracted source:
        ./configure && make && make install

    Windows:
    ---------
    On Windows, if you want to build the test GUI, you will need to get
    the hidapi-externals.zip package from the download site.  This
    contains pre-built binaries for Fox-toolkit.  Extract
    hidapi-externals.zip just outside of hidapi, so that
    hidapi-externals and hidapi are on the same level, as shown:

         Parent_Folder
           |
           +hidapi
           +hidapi-externals

    Again, this step is not required if you do not wish to build the
    test GUI.